Application of Supercritical Fluid Extraction in Biotechnology

ABSTRACT

In the present paper recent investigations on the applications of supercritical fluid extraction (SCE) from post fermentation biomass or in situ extraction of inhibitory fermentation products as a promising method for increasing the yield of extraction have been reviewed. Although supercritical CO₂ (SC-CO₂) is unfriendly, or even toxic, for some living cells and precludes direct fermentation in dense CO₂, it does not rule out other useful applications for in situ extraction of inhibitory fermentation products and fractional extraction of biomass constituents. This technique is a highly desirable method for fractional extraction of biomass constituents, and intracellular metabolites due to the potential of system modification by physical parameters and addition of co-solvents to selectively extract compounds of different polarity, volatility and hydrophilicity without any contamination.     

Isolation and characterization of allelochemicals in rye herbage

Residues and aqueous extracts of rye (Secale cereale L. ‘Wheeler’) shoot herbage were previously shown to contain phytotoxic compounds. Sequential partitioning of aqueous extracts against a series of solvents of increasing polarity separated the most active compounds in the Et₂O fraction based on a cress (Lepidium sativum L. ‘Curly’) root growth assay. Bioassays after TLC indicated two major zones of toxicity. Further separation of the Et₂O extract revealed two new phytotoxic compounds in rye. The compounds were identified as 2,4-dihydroxy-1,4(2H)-benzoxazin-3-one (DIBOA) and a breakdown product 2(3H)-benzoxazolinone (BOA). In the cress bioassay, DIBOA and BOA inhibited root growth 50% or more at concentrations of ca 0.37 and 1.05 mM, respectively. Only DIBOA showed significant activity on barnyardgrass (Echinochloa crusgalli L. Beauv.). Neither compound inhibited seed germination at concentrations tested. DIBOA stimulated root and shoot growth of cress at the lowest concentration tested (0.09 mM).     

Biochemical composition of Tunisian Nigella sativa L. at different growth stages and assessment of the phytotoxic potential of its organic fractions

The present study was conducted to study some biochemical characteristics of Tunisian Nigella sativa at different developmental stages of plant growth (vegetative, flowering and fruiting stages) and to screen the chemical constituents and the phytotoxic activity of their organic extracts on lettuce (Lactuca sativa L.). The GC–MS analysis of petroleum ether fractions revealed that N. sativa seeds were rich in linoleic acid (58% of total fatty acids), oleic acid (22% of total fatty acids) and palmitic acid (12% of total fatty acids). The fatty acid composition of aerial parts showed an increase in the level of saturated fatty acids accompanied by a concomitant decrease of polyunsaturated fatty acids levels during the developmental stage. The phytochemical investigation showed that among the organic extracts, the methanolic extract from aerial parts harvested at the fruiting stage contained the highest amounts of phenolic and flavonoid compounds. The phytotoxic study revealed that N. sativa negatively affected the growth of lettuce plants. This effect was largely dependent on the developmental stage at which material was collected and the nature of extracting solvent. The methanolic extract of aerial parts harvested at the vegetative stage was the most active on seedling growth of lettuce.     

The influence of macrophytes on a phytoplankton community in experimental conditions

The impact of submerged macrophytes or their extracts on planktonic algae was studied under experimental conditions. Live Ceratophyllum demersum L., its extract, and extracts of four other plant species induced modifications in the phytoplankton dominance structure. These modifications were: a decline in the number of Oscillatoria limnetica Lemm., which was the most numerous cyanobacterian species, and a decline in biomass and percentage contribution of all cyanobacteria to total algal biomass. This was accompanied by an increase in biomass and percentage contribution of green algae, especially Chlorella sp. and Chlamydomonas sp. Also, there was an increase in biomass and percentage contribution of nanoplankton (under 50 µm) to total phytoplankton biomass.The isolation of planktonic algae from direct influence of C. demersum by means of dialysis membranes caused an increase in number, biomass and percentage contribution of cyanobacteria. Release of organic compounds of over 3000 daltons by macrophytes apparently contributed to a decline of cyanobacteria by changing the phytoplankton dominance structure.     

Identification of vibriocidal compounds from medicinal plants using chromatographic fingerprinting

The aim of the present study was to investigate the vibriocidal activity of bark of Syzygium cumini, leaves of Lawsonia inermis, fruits of Terminalia bellerica and identify the bioactive compounds. The vibriocidal activity of plant extracts was determined in aqueous and organic solvents, and the minimum inhibitory concentration (MIC) against Vibrio spp. using the disk diffusion method was established. The chemical constituents of the plant extracts were analysed by thin layer chromatography (TLC), the vibriocidal compounds were determined by TLC-bioautography and were further confirmed by high performance liquid chromatography (HPLC). Significant inhibitory activity was observed with ethanol extract of plants against the test bacteria while less antibacterial activity was observed in acetone, methanol and aqueous extracts. The MIC of the plant extracts ranged between 2.5 and 20 mg/ml. The TLC, TLC-bioautography and HPLC analysis showed that gallic acid and tannin present in ethanol extracts of S. cumini, tannin present in L. inermis and gallic acid present in T. bellerica may be responsible for the vibriocidal activity. S. cumini, L. inermis and T. bellerica can be used for the treatment of gastroenteritis, diarrhoea and cholera diseases after detailed investigations. We also conclude that the plants rich in gallic acid and tannin can be used as an alternative to search for new vibriocidal drugs.     

Evaluation of phytotoxic potential and identification of phytotoxic compounds in Rumex maritimus

Rumex maritimus (Polygonaceae) is an annual herb and is well known for its use in medicinal treatments. Although the pharmacological properties of R. maritimus are well documented, no phytotoxic activity of R. maritimus has yet been found. Therefore, we investigated the phytotoxic potential of R. maritimus to identify phytotoxic compounds. Inhibitory activity was found in aqueous methanol extracts of R. maritimus on the seedling growth of cress, rapeseed, barnyard grass, and foxtail fescue, in which inhibition increased with increasing extract concentration. Two compounds were isolated using chromatography, and using spectroscopy their structure was determined as 5,7-dihydroxyphthalide and altechromone A. 5,7-Dihydroxyphthalide significantly inhibited cress seedling growth by 27.2–43.0% of control seedlings at 3 mM, whereas altechromone A inhibited seedling growth by 65.4–66.3% at 0.01 mM. The concentrations required for 50% inhibition of cress seedling growth were 1.73–2.48 mM for 5,7-dihydroxyphthalide and 0.66–1.41 mM for altechromone A. These results indicate that the compounds 5,7-dihydroxyphthalide and altechromone A may contribute, to a certain extent, to the phytotoxic activity of R. maritimus.     

Rapid transformations of plant water-soluble organic compounds in relation to cation mobilization in an acid Oxisol

The maintenance of plant residues on the surface of acid soils in no-tillage cropping systems reportedly increases the downward mobility of Ca and Al. This study investigated the effects of application of aqueous extracts of residues of radish (Raphanus sativus), blue lupine (Lupinus angustifolius), black oat (Avena strigosa), soybean (Glicine max), and wheat (Triticum aestivum), without incubation (initial extract) or incubated (15-day extract), on the chemistry of an acid Oxisol in 0.20-m columns. The application of initial extracts of plant residues increased the pH and the KCl-extractable contents of Ca²⁺, Mg²⁺ and Mehlich 1-extractable K⁺, and decreased the KCl-extractable Al³⁺ in the following order: blue lupine > radish > black oat > soybean > wheat. The Ca concentrations of the effluents, after application of the initial extracts of radish and blue lupine, were virtually the same as those in the extracts before application, whereas K was decreased by 40 – 90%, and more Al was extracted from the soil than the amount determined as KCl-extractable Al. The initial and 15-day extracts had similar effects on soil Ca and Al, however, the capacity of mobilizing Ca and Al was markedly decreased in the latter. This difference was associated with the type and relative composition of organic compounds in the water soluble organic fraction in both extracts as determined by gas chromatography–mass spectrometry (GC–MS). The concentration of water soluble organic compounds in the fresh green manures residues became drastically decreased (50% on average) after the incubation. The initial extracts of blue lupine and radish had a high proportion (20 and 30%, respectively) of the organic compounds as short-chain fatty acids with a high capacity of forming stable complexes with Ca and Al. In contrast, the 15-day extracts were predominated by long-chain fatty acids and aromatic compounds, which did not show the same effect. Fresh green-manure residues had water-soluble organic compounds of low molecular weight with high capacity of forming stable complexes with Ca and Al. The biological oxidation of these organic compounds occurred rapidly, markedly decreasing the capacity to mobilize cations in the aqueous plant-residue extracts.     

Qualitative HPLC‐DAD/ESI‐TOF‐MS Analysis,Cytotoxic, and Apoptotic Effects of Croatian Endemic Centaurea ragusina L. Aqueous Extracts

Centaurea ragusina L., an endemic Croatian plant species, revealed a good cytotoxic activity of aqueous extracts (AE) on human bladder (T24) and human glioblastoma (A1235) cancer cell lines. The chemical constituents were tentatively identified using high performance liquid chromatography HPLC‐DAD/ESI‐TOF‐MS in negative ionization mode. The main compounds of herba extract were sesquiterpene lactones: solstitialin A 3,13‐diacetate and epoxyrepdiolide; organic acid: quinic acid. The main compounds of flower extract were organic acids: quinic acid, citric acid, and malic acid; sesquiterpene lactone: cynaropicrin; phenolic compounds: chlorogenic acid and phenylpropanoid: syringin. The AE of C. ragusina were investigated for correlation of their effects on human bladder (T24) and human glioblastoma (A1235) cancer cell lines using the MTT assay. Although both extracts showed significant dose‐ and time‐dependent cytotoxic activity against both cancer cell lines, the flower extract exhibited slightly higher activity. In order to determine type of cell death induced by treatment, cell lines were exposed subsequently to a treatment with both flower and herba AE. The majority of the cells died by induced apoptosis treatment. Flower AE (26.25%), compared to a leaf AE (22.15%) showed slightly higher percentage of an apoptosis in T24 cells, when compared to a non‐treated cells (0.04%).     

Total phenolic content and antioxidant activity of plants used in traditional Romanian herbal medicine

A number of herbal plants from Romania widely used as natural food additives or for health promotion in traditional medicine were investigated for their antioxidant activity. Methanol extracts were obtained from plants belonging to the Lamiaceae family (lavender Lavandula angustifolia L.; lemon balm Melissa officinalis; sage Salvia officinalis; oregano Origanum vulgare L.; rosemary Rosmarinus officinalis L.; thyme Thymus vulgaris L.; mullein Verbascum phlomoides; mint Mentha longifolia), Clusiaceae family (St John’s wort Hypericum perforatum L.), and Compositae family (elecampane Inula helenium). Total phenolic concentration was determined using the Folin-Ciocalteu phenol reagent method, while total flavonoids were measured using the aluminium chloride colorimetric method. Relationships between total antioxidant activity and composition of plant extracts were evaluated. Origanum vulgare extract showed the highest antioxidant activity and total phenolic content compared to the other plants extracts. A positive correlation was observed between total antioxidant activity and total phenolic content of the analyzed extracts.     

Plant Growth Inhibitory Compounds from Aqueous Leachate of Wheat Straw

When seedlings of lettuce, cress, rice and wheat were incubated with the leachate of wheat straw, the roots growth of lettuce and garden cress were particularly inhibited. The leachate of wheat straw (100 g eq./l) showed 80.5 and 79.4% inhibition for lettuce and cress roots, respectively. The inhibitory activity was stronger as the concentration of wheat straw leachate was greater. This result indicates that allelochemical(s) inhibiting the roots growth of lettuce and cress are leached from the wheat straw into the water. Two potent compounds were isolated from the leachate of the wheat straw and identified as syringoylglycerol 9-O-β-d-glucopyranoside and l-tryptophan by spectral analyses. Syringoylglycerol 9-O-β-d-glucopyranoside inhibited the roots growth of lettuce and cress at concentrations greater than 0.1 and 10.0 μM, respectively. On the other hand, l-tryptophan inhibited the roots growth of lettuce and cress at concentrations greater than 0.1 and 1.0 μM, respectively. The content of syringoylglycerol 9-O-β-d-glucopyranoside and l-tryptophan in the leachate of wheat straw (100 g eq./l) was 18.4 ± 0.7 and 6.2 ± 0.6 μM, respectively. Syringoylglycerol 9-O-β-d-glucopyranoside (18.4 μM) showed 21.5 and 13.5% inhibition in the lettuce and cress roots assay, respectively. On the other hand, 6.2 μM of l-tryptophan showed 47.5 and 35.0% inhibition in the lettuce and cress roots assay, respectively. These results suggested that l-tryptophan may be a major contributor to the allelopathy in aqueous leachate of wheat straw and syringoylglycerol 9-O-β-d-glucopyranoside may be a minor contributor.     

Phytochemical Screening,Antioxidant Assay and Cytotoxic Profile for Different Extracts of Chrysopogon zizanioides Roots

The Chrysopogon zizanioides plant possesses multiple traditional uses, especially in therapeutics, but only a few articles have reported its biological activity. Hence, the present study was planned to explore the phytochemical constituents, cytotoxic potential, radical scavenging activity, and GC/MS (Gas chromatography & Mass spectrometry) analysis of the vetiver root extracts. The roots extracted with different solvents exhibited more significant phytochemical constituents in polar solvents in comparison to non-polar ones, favoring the extraction of a greater number of components in highly polar solvents. All the extracts were tested for their cytotoxicity using SRB (Sulforhodamine B) assay. They confirmed ethanolic extract as a potent extract with GI₅₀ 56±0.5 μg/ml in oral cancer (SCC-29B) along with no cytotoxicity in healthy cells (Vero cells), making it a safer therapeutic option in comparison to standard Adriamycin. This extract was also analyzed for its antioxidant potential by DPPH (1,1-Diphenyl-2-picrylhydrazyl) assay with IC₅₀ value 10.73 μg/ml, which was quite comparable to Ascorbic acid having IC₅₀ value 4.61 μg/ml. The quantitative analysis of ethanolic extract exhibited 107 compounds amongst which Khusenic acid, Ascorbic acid, Junipen, gamma-Himachalene, alpha-Guaiene were the majorly occurring compounds that can be explored further for their cytotoxic activity.     

Phenolic compounds and antioxidants from Eucalyptus camaldulensis as affected by some extraction conditions,a preparative optimization for GC-MS analysis

Abstract

Four organic solvents along with water were applied for the conventional extraction of Eucalyptus camaldulensis (Myrtaceae), phenolic contents and antioxidant activities were investigated through variable protocols and correlation coefficients were considered, the phenolic composition was also characterized by Gas chromatography-mass spectrometry (GC-MS). Using solvents with dissimilar polarities affected the phenolic yields extracted from E. camaldulensis and their related antioxidant activities varied significantly among the four investigated plant organs. The leaf extract of acetone 70% contained the highest amount of phenolic compounds (46.56?mg/g dry weight); while the bud-water boiled extract maintained the maximum value of tannins (45.68?mg/g dry weight). Correlation coefficients indicated that phenolic compounds were mostly accountable for the phosphomolybednum antioxidant potentials (0.520), followed by tannins (0.460). Also, both the reducing power activities and hydrogen peroxide scavenging of E. camaldulensis extracts positively correlated with tannins, but at different significance degrees. However, the GC-MS analysis revealed that most of the detected phenolic constituents were more abundant in the plant seed. So, the existence of some other compounds such as organic acids, along with phenolics, may have increased the antioxidant potentials of leaf and bud. Undeniably, the optimization of extraction conditions could stimulate the antioxidant capabilities of the plant extracts of E. camaldulensis.     

Phytochemical Content,Antidiabetic, Anticholinergic,and Antioxidant Activities of Endemic Lecokia cretica Extracts

The aim of this work was to investigate the enzyme inhibition, antioxidant activity, and phenolic compounds of Lecokia cretica (Lam .) DC. Acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and α‐glycosidase enzymes were strongly inhibited by the L. cretica extracts. IC₅₀ values for the three enzymes were found as 3.21 mg/mL, 2.1 mg/mL, and 2.07 mg/mL, respectively. Antioxidant activities were examined in both aqueous and ethanol (EtOH) extracts using CUPRAC, FRAP, and DPPH method. Also, the phenolic compounds of the endemic plant were identified and quantified by using HPLC/MS/MS. According to the results, the extracts have remarkable antioxidant activities. The most abundant phenolic acids of L. cretica in EtOH extract were determined as quinic acid (12.76 mg/kg of crude extract), chlorogenic acid (3.39 mg/kg), and malic acid (2.38 mg/kg).     

Isolation and identification of a plant growth inhibitor from Tinospora tuberculata Beumee

Tinospora tuberculata Beumee has been used widely as a folk medicine and several bioactive compounds have been isolated. However, no herbicidal compound has been reported in this species. Therefore, we investigated the presence of phytotoxins in T. tuberculata. The aqueous methanol extracts of T. tuberculata inhibited the growth of roots and shoots of cress (Lepidum sativum L.), lettuce (Lactuca sativa L.), timothy (Phleum pratense L.) and barnyard grass (Echinochloa crus-galli (L.) Beauv.). The extract was then purified by several chromatographic runs with monitoring the inhibitory activity and the main phytotoxic substance was isolated. The chemical structure of the compound was determined by spectral data as syringin (4-[(1E)-3-Hydroxyprop-1-en-1-yl]-2,6-dimethoxyphenyl β-d-glucopyranoside). It inhibited the root and shoot growth of all test plant species at concentrations >10 µM. The concentrations required for 50 % inhibition of root and shoot growth of cress and lettuce ranged from 78.2 to 412 μM, and that of timothy and barnyard grass renged from 9.8 to 73.2 µM. Effectiveness of syringin on monocotyledonous (timothy and barnyard grass) plants was greater than that on dicotyledonous (cress and lettuce) plants. These results suggest that syringin may contribute to the allelopathic effect caused by the T. tuberculata extract.     

Characterisation of biological properties of co‐composted Baltic seaweeds in germination tests

Large quantities of green seaweed, probably due to eutrophication, are found in the Baltic Sea, as well as on the beach. The tourist attractiveness of the seaside resorts is therefore reduced. The aim of this study was to find the method of the utilization of this algal biomass into fertilizers. Algae, collected from the Baltic Sea, were co‐composted with sawdust and quail manure in order to produce natural fertilizer. From the compost, algal extract was additionally produced that can act as a plant growth biostimulant. The compost and extract were biologically evaluated by the determination of the growth and multielemental composition of garden cress (Lepidium sativum) in germination tests. Additionally, the odour emissions during composting process were investigated. It was found that the dry biomass was comparable in all examined groups (compost, extract, distilled water). The average length of plants in the group with compost was 14.5% higher than in the group with the extract (difference not statistically significant). There has been observed a positive effect of the addition of compost on the content of micro‐ and macronutrients in the biomass of the cultivated plants, especially boron, calcium, iron and silicon. The averaged odour concentrations measured from the compost and extract samples were very low and reached the values of 8 and 24 ou_E/m³, respectively. According to the obtained results, by composting of seaweeds it is possible to produce a valuable organic fertilizer, which is the method of valorisation of this biomass.     

Anti-diabetic properties of three common Bidens pilosa variants in Taiwan

Bidens pilosa L. var. radiata (BPR), B. pilosa L. var. pilosa (BPP), and B. pilosa L. var. minor (BPM) are common variants of a plant often used as a folk remedy for diabetes in Taiwan. However, the three variants are often misidentified and little is known about their relative anti-diabetic efficacy and chemical composition. In this paper, we have first developed a method based on GC–MS and cluster analysis with visualization to assist in rapidly determining the taxonomy of these three Bidens variants. GC–MS was used to determine the chemical compositions of supercritical extracts, and differences and similarities in the variants were determined by hierarchical cluster analysis. Next, the HPLC profiles of the methanol crude extracts in the Bidens plants and evaluated anti-diabetic effects of methanol crude extracts were compared, as well as three polyacetylenic compounds of the Bidens plants using db/db mice. Single-dose and long-term experiments showed that the BPR extract had higher glucose-lowering and insulin-releasing activities than extracts from the other two variants, and that cytopiloyne was the most effective pure compound among the three polyacetylenic compounds. BPR extract and cytopiloyne also significantly reduced the percentage of the glycosylated hemoglobin A1c in db/db mice. Besides, both animal studies and HPLC analysis demonstrated a good correlation between anti-diabetic efficacy of the Bidens extracts and the particular polyacetylenes present.     

Comparative analysis of the cytotoxic activity of extracts from different parts of A. absinthium L. on breast cancer cell lines and correlation with active compounds concentration

The aim of the present study was to compare the cytotoxicity of different extracts of the plant Artemisia absinthium on breast cancer cell lines and to establish the correlation between the cytotoxicity and the active constituent’s level in these extracts. The cytotoxicity of the extracts was evaluated on the breast cancer cell lines, MCF-7 and MDA MB-231 by MTT assay and LDH release assay. An HPTLC method was developed for the simultaneous estimation of active constituents, that is, artemisinin, artemisinic acid, and alpha-thujone in different parts of A. absinthium. The whole extract was best among all the extracts tested with least IC₅₀ value and high LDH release that is, 491.19?µg/µL with 27.92% for MCF-7 and 459.97?µg/µL with 29.43% for MDA MB-231 cell lines respectively. Although, the concentration of all three quantified active compounds was higher in the extract from aerial part; however, the whole extract showed the best cytotoxicity among all extracts evaluated on the breast cancer cell lines. Surprisingly, our results demonstrate that the quantified active compounds were not solely responsible for the cytotoxic activity of the plant parts and further studies may be conducted to identify the compounds with synergistic, allosteric or antagonistic effects.     

Phytochemical and Biological Activities of Pseudocalymma elegans: A False Garlic

Evaluation of phytochemical constituents and antioxidant and antimicrobial activities of hexane (PELH), dichloromethane (PELDCM), ethyl acetate (PELEA), and MeOH (PELM) extracts of young leaves of Pseudocalymma elegans have been carried out. Moreover, extracts have also been explored for the presence of sulphur containing compounds, 1,2‐dithiolane ( 33 ), diallyl disulfide ( 35 ), 3‐vinyl‐1,2‐dithiacyclohex‐5‐ene ( 37 ), and diallyl trisulfide ( 38 ) responsible for the garlic like smell of P. elegans. All the extracts were found to be antioxidant and showed potent inhibition with IC₅₀ values of 0.168 ± 0.001, 0.128 ± 0.002, 0.221 ± 0.011, and 0.054 ± 0.001, respectively, as compared to standard drugs ascorbic acid (AA) and butylated hydroxytoluene (BHT). The ethyl acetate extract (PELE) showed excellent activities against few Gram‐positive and Gram‐negative bacteria and some fungi as compared with standard drug ceftriaxone (3rd generation cephalosporin) and nystatin, respectively. Chemical constituents of hexane, dichloromethane, and ethyl acetate extracts were identified by gas chromatography‐mass spectrometry and mass spectral library search. Over all 55 chemical constituents were first time identified from the leaves which included branched and n‐hydrocarbons, fatty acids, fatty acid methyl esters, fatty alcohols, terpenes, alkaloid, vitamins, glycosides, aromatic compounds, and sulfur containing compounds. Two known chemical constituents, ursolic acid ( 1 ) and β‐amyrin ( 2 ), were also purified for the first time from the MeOH extract. To elucidate the structures of these compounds, UV, IR, EI‐MS, ¹H‐ and ¹³C‐NMR spectroscopy were used.     

A novel allelopathic substance, 13-epi-orthosiphol N,in Orthosiphon stamineus

Orthosiphon stamineus (Java tea) has been widely used as traditional herb and several bioactive compounds against animal cells have been isolated. However, no bioactive compound against plants has been reported. Therefore, we investigated possible allelopathic properties and substances in O. stamineus. Aqueous methanol extracts of O. stamineus inhibited root and hypocotyl growth of cress (Lepidium sativum) and lettuce (Lactuca sativa) seedlings. Increasing the extract concentration increased the inhibition, which suggests that O. stamineus may have allelopathic properties. When the extract was divided into an ethyl acetate and an aqueous fraction, the ethyl acetate fraction showed the stronger inhibitory effect. Thus, the ethyl acetate phase was further purified, and the main allelopathic substance was isolated and identified as 13-epi-orthosiphol N, a novel compound, by spectral data. 13-epi-Orthosiphol N inhibited root and hypocotyl growth of cress and lettuce at concentrations greater than 10 μmol/L. The concentrations required for 50% inhibition ranged from 41 to 102 μmol/L. These results suggest that 13-epi-orthosiphol N may be an allelochemical and main contributor to the growth inhibitory effect of O. stamineus and may have potential as a template for the development of new plant control substances.     

Cordeauxia edulis and Rhododendron tomentosum extracts disturb orientation and feeding behavior of Hylobius abietis and Phyllodecta laticollis

The use of plant‐based compounds to control insect pests is an alternative to the use of synthetic pesticides. We evaluated the repellent and antifeedant effects of Cordeauxia edulis Hemsley (Fabaceae) and Rhododendron tomentosum Harmaja (Ericaceae) extracts against Hylobius abietis L. (Coleoptera: Curculionidae) and Phyllodecta laticollis Suffrian (Coleoptera: Chrysomelidae). Repellent properties were evaluated by monitoring responses of adult insects toward the odor from extracts or extraction solvents (controls) in a Y‐tube olfactometer, and choice or no‐choice feeding tests were conducted by applying extracts or extraction solvents on stems of Scots pine [Pinus sylvestris L. (Pinaceae)] and European aspen [Populus tremula L. (Salicaceae)], host plants of H. abietis and P. laticollis, respectively. Extracts of R. tomentosum repelled adults of both insect species effectively. However, extracts of C. edulis did not repel H. abietis although its ethyl acetate extract showed repellence against the adults of P. laticollis. Feeding by H. abietis was significantly reduced by a methanol extract of C. edulis, and methanol and hexane extracts of R. tomentosum. Feeding by the adults and larvae of P. laticollis was significantly reduced by extracts from both plant species. Concomitant with less feeding, larval growth was retarded by ethyl acetate extracts of both plant species. Gas chromatography‐mass spectrometry analyses of the volatile components of the extracts showed that extracts from both plant species were mixtures of various terpene and non‐terpene compounds, which showed quantitative and/or qualitative variations between plant species and extraction solvents. This experiment showed that extracts from both plant species effectively manipulated the orientation and/or feeding behavior of the two beetle species. Hence, they may be considered as potential alternatives to synthetic chemical pesticides.