柑桔果实中柠檬苦素类化合物的研究现状与展望

柠檬苦素类似物（ｌｉｍｏｎｏｉｄ）是三萜类的植物次生代谢产物,主要存在于芸香科和楝科植物中。柠檬苦素（ｌｉｍｏｎｉｎ）及其类似物存在于柑桔属（Ｃｉｔｒｕｓ）的多种植物中。至今已从柑桔属植物中分离出３６种柠檬苦素类似物及１７种柠檬苦素类似物配糖体。柑桔中苦味原因之一为柠檬苦素类似物。作为其代表具有强烈苦味的柠檬苦素和诺米林如果在柑桔果汁中含量超过６ｍｇ／Ｌ,那么这种柑桔用于饮食业已不适合［１］。近年来,笔者对柑桔果实中的柠檬苦素类似物的生理变化及生物合成作过系统研究［１～９］,并提出将柠檬苦素类似…     

The Prospect and Current Studies on the Limonoids in Citrus

Limonoids are a group of triterpenoids found in Rutaceae and Meliaceae. Limonoids of citrus are excellent physiologically active compounds. In this paper, we report the biochemical study and biological recovery of limonoids in citrus fruits.     

Antimalarial activity of anthothecol derived from Khaya anthotheca (Meliaceae)

Antimalarial activity of anthothecol, a limonoid of Khaya anthotheca (Meliaceae) against Plasmodium falciparum was tested using a [³H]-hypoxanthine and 48 h culture assay in vitro. Anthotechol showed potent antimalarial activity against malaria parasites with IC₅₀ values of 1.4 and 0.17 μM using two different assays. Also, gedunin had antimalarial activity with IC₅₀ values of 3.1 and 0.14 μM. However, the citrus limonoids, limonin and obacunone did not show any antimalarial activity. The antimalarial activities were compared with the three currently used antimalarial medicines quinine, chloroquinine and artemisinin.     

Limonoids from the genus Trichilia and biological activities: review

Phytochemistry Reviews - Limonoids, present in the families Meliaceae and Rutaceae, provide the bitter principles in citrus and are derived from limonin (first isolated tetranortriterpenoid). These...     

Limonoid derivatives and its pesticidal activities

Diverse pesticidal activities of anthothecol derived from Khaya anthotheca (Meliaceae) and three limonoids (gedunin, limonin and obacunone) were determined using six phytopathogenic fungi and four insect pests. Anthothecol showed fungicidal activity to Puccinia recondita with control rates of 90, 76 and 53% at concentrations 0.5, 0.25 and 0.1 mg/mL, respectively, while the other limonoids exhibited little inhibitory effect on the fungal survival. The currently used fungicide mancozeb possessed potent fungicidal activity on P. recondite, with 92.3% controlling effect at a concentration of 0.005 mg/mL. Anthothecol exhibited larvicidal activity to Plutella xylostella with 80, 50 and 30% mortality at concentrations of 1.0, 0.5 and 0.25 mg/mL, respectively. Anthothecol showed selective pesticidal activity on P. recondita and P. xylostella. Structural re‐examination of anthothecol was conducted and is reported.     

Production of biopesticide azadirachtin using plant cell and hairy root cultures

The extensive use of nondegradable chemical pesticides for pest management has developed serious environmental hazards. This has necessitated the urgent need to switch over to an alternative mode of biopesticide development for mass agriculture and field crop protection. Azadirachta indica A. Juss (commonly known as neem) houses a plethora of bioactive secondary metabolites with azadirachtin being the most active constituent explored in the sector of ecofriendly and biodegradable biopesticides characterized by low toxicity toward nontarget organisms. It has been reported that the highest content of azadirachtin and related limonoids is present in the seeds, available once in a year. Moreover, the inconsistent content and purity of the metabolites in whole plant makes it imperative to tap the potential of in vitro plant tissue culture applications, which would allow for several controlled manipulations for better yield and productivities. This review gives a summarized literature of the applied research and achievements in plant cell/hairy cultures of A. indica A. Juss mainly in context with the biopesticide azadirachtin and applications thereof.     

Characterization of Limonoids Isolated from the Fruits of Melia toosendan and Their Antifeedant Activity against Pieris rapae

The fruits of Melia toosendan Sieb . et Zucc . (Meliaceae) are a source of bioactive limonoids that can be used as effective pesticides. In this study, two novel limonoids, 6‐acetylsendanal and 6‐ketocinamodiol, were isolated together with fourteen known compounds, namely four protolimonoids, six trichilin‐class limonoids, and four C‐seco limonoids. The structures of the new compounds were determined by extensive spectroscopic analyses (HR‐ESI‐MS, UV, IR, 1D and 2D NMR). The bioassay results revealed that eleven of the extracted limonoids exhibited interesting antifeedant activities against the larvae of Pieris rapae with AFC₅₀ values in the range of 0.11–1.79 mm . Particularly, mesendanin H, with an AFC₅₀ value of 0.11 mm , exhibited a higher activity than the positive control toosendanin. Information on new bioactive limonoids may provide further insight into M. toosendan as a source of bioactive components.     

Differential thresholds of azadirachtin for feeding deterrence and toxicity in locusts and an aphid

Conclusions The importance of using azadirachtin in the field at levels causing primary antifeedancy may have been overemphasised in the past. Currently, it is recommended that commercial preparations of neem be applied at 50–100 ppm (a.i.). While this would undoubtedly have an antifeedant effect in many phytophagous insects it may also harm beneficial species (Schmutterer, 1990). By lowering the concentration of azadirachtin applied to the crop, food intake by insect pests with low chemoreceptor sensitivity to azadirachtin, e.g. aphids (Nisbet et al., 1993; 1994), would not initially be affected. However, secondary antifeedant effects, IGR and sterilant effects could rapidly manifest themselves and bring about crop protection by reducing insect pest populations without harming natural predator or parasitoid populations.     

Nitric Oxide Production‐Inhibitory Activity of Limonoids from Azadirachta indica and Melia azedarach

Seventy‐three limonoids isolated from three Meliaceae plants, Azadirachta indica, A. indica var. siamensis, and Melia azedarach, or semi‐synthesized from the Meliaceae limonoids, were evaluated for their inhibitory activity against nitric oxide (NO) production in mouse macrophage RAW 264.7 cells induced by lipopolysaccharide (LPS), as a primary screening test for anti‐inflammatory agents. Of the compounds tested, 21 compounds exhibited inhibitory activity (IC₅₀ 4.6 – 58.6 μm ) without any significant toxicity (IC₅₀ > 100 μm ) which were more potent than l ‐NMMA (NO‐production inhibitory activity, IC₅₀ 65.6 μm ; cytotoxicity, IC₅₀ > 100 μm ), and among which, nine compounds, i.e., 17‐hydroxy‐15‐methoxynimbocinol ( 6 ), ohchinin ( 20 ), 1‐cis‐cinnamoyl‐1‐decinnamoylohchinin ( 24 ), salannin ( 27 ), methyl nimbidate ( 32 ), isosalannin ( 55 ), nimbolinin D ( 58 ), mesendanin E ( 69 ), and 7‐deacetylgedunin ( 73 ) exhibited potent inhibitory activity (IC₅₀ 4.6 – 29.3 μm ). In particular, compounds 6 (IC₅₀ 7.3 μm ), an azadirone‐type limonoid, and 73 (IC₅₀ 4.6 μm ), a gedunin‐type limonoid, exhibited remarkable activity. Western blot analysis revealed that 27 and 73 reduced the expression levels of the inducible NO synthase and cyclooxygenase‐2 proteins in a concentration‐dependent manner. These findings suggest that limonoids of A. indica, A. indica var. siamensis, and M. azedarach, and their semi‐synthetic derivatives may be effective against inflammation.     

Three New and Other Limonoids from the Hexane Extract of Melia azedarach Fruits and Their Cytotoxic Activities

A defatted fraction obtained from the hexane extract of the fruits of Melia azedarach L. (chinaberry tree; Meliaceae) exhibited cytotoxic activities against leukemia (HL60), lung (A549), stomach (AZ521), and breast (SK‐BR‐3) cancer cell lines with IC₅₀ values in the range of 2.9–21.9 μg/ml. Three new limonoids, 3‐deacetyl‐4′‐demethylsalannin ( 5 ), 3‐deacetyl‐28‐oxosalannin ( 14 ), and 1‐detigloylohchinolal ( 17 ), along with 16 known limonoids, 1 – 4, 6 – 13, 15, 16, 18 , and 19 , and one known triterpenoid, 20 , were isolated from the fraction. The structures of new compounds were elucidated on the basis of extensive spectroscopic analyses and comparison with literature. These compounds were evaluated for their cytotoxic activities against the four cancer cell lines mentioned above. 3‐Deacetyl‐4′‐demethyl‐28‐oxosalannin ( 16 ), which exhibited potent cytotoxicity against AZ521 (IC₅₀ 3.2 μM ) cells, induced typical apoptotic cell death in AZ521 cells upon evaluation of the apoptosis‐inducing activity by flow cytometry. This work provided, furthermore, valuable information on the structural features of limonoids of the fruits and/or seeds of Melia azedarach and related Meliaceae plants, M. toosendan and Azadirachta indica.     

In vitro egg hatching of Diaphorina citri,the vector of Huanglongbing

Citrus greening (Huanglongbing, HLB) is a destructive disease associated with the uncultivable, phloem-limited, gram-negative bacteria Candidatus Liberibacter spp., which affects citrus crops and other Rutaceae species. HLB is rapidly transmitted by the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae). We developed an artificial medium on which D. citri eggs can hatch and first-instar nymphs can feed. The medium could be used to study insect physiology and screen molecules that may interfere with egg hatching and nymph development.     

Larvicidal activities of limonoids from Turraea abyssinica (Meliaceae) on Tuta absoluta (Meyrick)

Preliminary screening of extracts of the leaves and stems of four Turraea plant species (Meliaceae) on second instar larvae of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) showed that the methanolic extract of Turraea abyssinica leaves possess good toxic potential with LD₅₀ of 270.7 ppm. Fractionation of this extract led to isolation of a new limonoid derivative, 12α‐diacetoxywalsuranolide (1) and three other known limonoids [1α,7α,12α‐triacetoxy‐4α‐carbomethoxy‐11β‐hydroxy‐14β,15β‐epoxyhavanensin (2), 11‐epi‐21‐hydroxytoonacilide (3), 11β,12α‐diacetoxycedrelone (4)]. The structures of the compounds were established by IR, UV, mass spectrometry and 1D/2D NMR analyses, and in the case of the known compounds, also by comparison with reported data. All the isolates were tested for their larvicidal activities at different dose range against second instar larvae of T. absoluta. They were found to be more active (with LD₅₀ < 7.0 ppm) compared to the reference compound azadirachtin (LD₅₀ value of 7.8 ppm).     

Limonoids and triterpenoids from the seed of Neobeguea mahafalensis

Three triterpenoids, sapelin C, sapelin E acetate and grandifoliolenone, were isolated from the hexane extract of the seed shells of Neobegueae mahafalensis (Meliaceae). The ethyl extract of the seed yielded the known limonoids, methyl angolensate, mexicanolide and khayasin.     

Limonoids from the stems of Toona ciliata var. henryi (Meliaceae)

Ten limonoids, toonacilianins A-J, and two norlimonoids, toonacilianins K and L, together with seven known compounds were isolated from the stems of Toona ciliata var. henryi (Meliaceae). Their structures were elucidated by spectroscopic analysis. Two compounds showed strong cytotoxic activities.     

Rings B,D-seco limonoids from the leaves of Swietenia mahogani

Seven phragmalin limonoids of swietephragmins A-G, and two other different types of 2-hydroxy-3-O-tigloylswietenolide and deacetylsecomahoganin, were isolated along with three known limonoids from the leaves of Swietenia mahogani (Meliaceae). Their structures were determined by spectroscopic methods.     

A COMPREHENSIVE STUDY ON APOPTOSIS INDUCTION BY AZADIRACHTIN IN Spodoptera frugiperda CULTURED CELL LINE Sf9

The induction of apoptosis by azadirachtin, a well‐known botanical tetranortriterpenoid isolated from the neem tree (Azadirachta indica A. Juss) and other members of the Meliaceae, was investigated in Spodoptera frugiperda cultured cell line (Sf9). Morphological changes in Sf9 cells treated by various concentrations of azadirachtin were observed at different times under light microscopy. Morphological and biochemical analysis indicated that Sf9 cells treated by 1.5 μg/mL azadirachtin showed typical morphological changes, which were indicative of apoptosis and a clear DNA ladder. The flow cytometry analysis showed the apoptosis rate reached a maximum value of 32.66% at 24 h with 1.5 μg/mL azadirachtin in Sf9 cells. The inhibition of Sf9 cell proliferation suggested that the effect of azadirachtin was dose dependent and the EC₅₀ at 48 and 72 h was 2.727 × 10⁻⁶ and 6.348 × 10⁻⁹ μg/mL, respectively. The treatment of azadirachtin in Sf9 cells could significantly increase the activity of Sf caspase‐1, but showed no effect on the activity of Topo I, suggesting that the apoptosis induced by azadirachtinin Sf9 cells is through caspase‐dependent pathway. These results provided not only a series of morphological, biochemical, and toxicological comprehensive evidences for induction of apoptosis by azadirachtin, but also a reference model for screening insect cell apoptosis inducers from natural compounds.     

The neem limonoids azadirachtin and nimbolide induce cell cycle arrest and mitochondria-mediated apoptosis in human cervical cancer (HeLa) cells

Abstract

Limonoids from the neem tree (Azadirachta indica) have attracted considerable research attention in recent years owing to their potent antioxidant and anti-proliferative effects. The present study was designed to investigate the cellular and molecular mechanisms by which azadirachtin and nimbolide exert cytotoxic effects in the human cervical cancer (HeLa) cell line. Both azadirachtin and nimbolide significantly suppressed the viability of HeLa cells in a dose-dependent manner by inducing cell cycle arrest at G0/G1 phase accompanied by p53-dependent p21 accumulation and down-regulation of the cell cycle regulatory proteins cyclin B, cyclin D1 and PCNA. Characteristic changes in nuclear morphology, presence of a subdiploid peak and annexin-V staining pointed to apoptosis as the mode of cell death. Increased generation of reactive oxygen species with decline in the mitochondrial transmembrane potential and release of cytochrome c confirmed that the neem limonoids transduced the apoptotic signal via the mitochondrial pathway. Altered expression of the Bcl-2 family of proteins, inhibition of NF-κB activation and over-expression of caspases and survivin provide compelling evidence that azadirachtin and nimbolide induce a shift of balance toward a pro-apoptotic phenotype. Antioxidants such as azadirachtin and nimbolide that can simultaneously arrest the cell cycle and target multiple molecules involved in mitochondrial apoptosis offer immense potential as anti-cancer therapeutic drugs.     

Photochemical Isomerization of Leaf Aldehyde

Isopimpinellin, bergapten, xanthotoxin, kokusagine, evoxine and japonin were isolated and identified in the leaves of Orixa japonica (Rutaceae) as feeding inhibitors against Spodoptera litura F. (Noctuidae). Isopimpinellin exhibited the most potent activity among above substances at the feeding inhibitory test. The isolated evoxine was the optical antipode of the previously reported one.