Plant responses and herbivory following simulated browsing and stem cutting of Combretum apiculatum

Abstract. Time and mode of herbivory on savanna trees and their subsequent responses are dependent on, among other things, earlier herbivory and fire. We used clipping (simulated browsing) and stem cutting (simulated heavy browsing and to some extent simulated fire) to evaluate such interactions. Study organisms were a deciduous, broad‐leaved tree species, Combretum apiculatum (Combretaceae), browsing large herbivores and leaf‐eating insects. The treatments were done in the late dry season before bud break. Late in the following wet season, we recorded plant responses to treatment and browsing. The treated trees, especially the cut ones, responded by producing larger and fewer annual shoots. Compared to control trees, there was a slight increase in shoot biomass of clipped trees and a strong reduction of cut ones. Leaf area increased in clipped trees, but decreased in cut ones. A marked increase in the number of browsed trees was recorded amongst treated trees. Number of bites, consumption and utilization also increased with severity of treatment. In contrast, insect herbivory was reduced on both clipped and cut trees. The observed patterns are discussed in relation to current ideas on plant ‐ herbivore interactions.     

Effect of eland density and foraging on Combretum apiculatum physiognomy in a semi-arid savannah

We studied the impacts of eland density on the physiognomy of Combretum apiculatum . We divided the study area into two zones: high eland density zone (≤8 km from watering point) and low eland density zone (≥8 km from watering point). Eland density was determined in each zone using walking transects. Combretum apiculatum height and diameter and levels of eland damage were measured in each zone. Eland density was 1.92 and 0.86 km⁻² for high and low-density zones respectively. We recorded 239 C. apiculatum trees, 138 in low-density zone and 101 in high-density zone. Mean C. apiculatum height was 2.88 ± 0.67 m and 5.05 ± 1.04 m for high and low eland density zones respectively. High eland density prevented the recruitment of C. apiculatum from the 2.6–5.5 m height class to the >5.6 m height class. Although extensive tree damage occurred at <2.5 m height stratum, C. apiculatum showed resilience as recruitment into the 2.6–5.5 m height class continued. We concluded that high eland density prevents recruitment of C. apiculatum to higher height classes while at the same time causing extensive tree damage at lower height strata.     

短角湿生冷水花化学成分的研究

为研究短角湿生冷水花(Pilea aquarum subsp.brevicornuta)化学成分。实验采用色谱法从中分离得到7个化合物,包括5个五环三萜、一个甾醇和一个木脂素。利用波谱学方法鉴定了它们的结构,分别鉴定为pilearbornol(1)、rubiarbonone D(2)、camarolide(3)、表齐墩果酸(4)、齐墩果酮酸(5)、5,8-epidioxy-(3β,5α,8α,22E)-ergosta-6,9(11),22-trien-3-ol(6)和桉脂素(7)。其中,化合物1和2属于乔木萜烷型(arborane)三萜,化合物1为新化合物,化合物2的绝对构型首次通过X-射线单晶衍射得到了确定。所有化合物均为首次从该植物中分离得到,这也是首次从荨麻科植物中分离得到乔木萜烷型三萜化合物。     

Isolation of an endoglucanase gene from Bacteroides ruminicola subsp. brevis

A gene coding for endo-1, 4-beta-glucanase activity has been isolated from Bacteroides ruminicola subsp. brevis by cloning in Escherichia coli. After restriction mapping of a 6.4 kb insert, a 2.2 kb DNA fragment was sub-cloned in pUC19 to produce the enzymically active clone pJW3. Recloning of the gene fragment in the reverse orientation in pUC18 (clone pJW4) indicated that a gene promoter was present in the cloned fragment and was able to function in E. coli. The clone pJW4 displayed increased activity which was attributed to expression from the lac promoter of pUC18. The enzyme encoded by pJW4 was optimally active at pH 5.5-6.0, and in the temperature range 37-42 degrees C. The preferred substrate was carboxymethylcellulose, but the enzyme displayed 50-60% of maximal activity on both acid-swollen cellulose and soluble xylan. No significant activity was detected on ball-milled filter paper or particulate xylan. Deletion experiments confirmed that both cellulase and xylanase activities were altered to a similar extent by deletion of DNA from the 3' end of the gene, suggesting that both are a function of the same polypeptide product.     

Cyclobutanes from Combretum albopunctatum

A dichloromethane extract of the aerial parts of Combretum albopunctatum Suesseng afforded five phenolic compounds-three known flavonoids and two novel cyclobutane chalcone dimers. The chemical structures were determined by standard spectroscopic techniques and the structure and relative stereochemistry of one chalcone dimer, rel-(1 alpha,2 beta)-di-(2,6-dimethoxy-4-hydroxy)-benzoyl-rel-(3 alpha,4 beta)-diphenylcyclobutane, were confirmed by single crystal X-ray diffraction.     

Anti-proliferative and antioxidant constituents from Tecoma stans

Phytochemical investigation of Tecoma stans Juss. fruits and flowers resulted in the isolation of a new phenylethanoid, 2-(3,4-dihydroxyphenyl)ethyl-2-O-[6-deoxy-alpha-L-mannopyranosyl-4-(3,4-dihydroxyphenyl)-2-propenoate]-beta-D-glucopyranoside (3), and a novel monoterpene alkaloid, 5-hydroxy-skytanthine hydrochloride (8), along with eleven known compounds; 4-O-E-caffeoyl-alpha-L-rhamnopyranosyl-(1' --> 3)-alpha/beta-D-glucopyranose (1), E/Z-acetoside (2), isoacetoside (4), rutin (5), luteolin 7-O-beta-D-neohespridoside (6), luteolin 7-O-beta-D-glucopyranoside (7) and sucrose (9) were isolated from the fruits, while luteolin 7-O-beta-D-glucuronopyranoside (10), diosmetin 7-O-beta-D-glucuronopyranoside (11), diosmetin 7-O-beta-D-glucopyranoside (12), diosmetin 7-O-beta-D-glucuronopyranoside methyl ester (13) and acetoside (2) were isolated from the flowers. Their chemical structures have been determined on the basis of chemical and spectroscopic evidences. Biological investigations of a T. stans fruits extract and compounds 1, 2, 4, and 8 indicated that the extract, 1, 2, and 4 possessed a strong scavenging activity to DPPH, peroxyl and hydroxyl radicals. Unlike 4, which potentially induced NO generation in bacterial lipopolysaccharide-stimulated raw murine macrophage (RAW 264.7), the extract, 1, 2, and 8 significantly inhibited the NO generation. The extract, 2 and 4 exhibited a cytotoxic effect on human hepatocarcinoma cells (Hep-G2), while the extract, 2 and 8 were potent growth inhibitors of human breast carcinoma cells (MCF-7). 1 and 2 were remarkable growth inducers of human lymphoblastic leukemia cells (1301), whereas the extract, 2, and 8 stimulated the macrophage proliferation rate. Taken together, the novel compound 8 is effective as anti-proliferative agent against MCF-7 cells and as NO inhibitor, whereas 2 exhibited multi-functional properties as antioxidant and anti-proliferative agent against both solid tumor cell lines Hep-G2 and MCF-7 cells.     

Chemical constituents isolated from Clusia criuva subsp. Criuva and their chemophenetics significance

Clusia criuva belongs to the Clusiaceae family and it is endemic to the rupestrian fields in Chapada Diamantina National Park (Brazil). Phytochemical investigation of C. criuva trunks led to the isolation of five triterpenoids [winchic acid (1), betulinic acid (2), lupeol (3), friedelin (4), and friedelinol (5)], four steroids [lanosterol (6), stigmasterol (7), β-sitosterol (8), and sitostenone (9)], seven polyprenylated benzophenone derivatives [propolone A (10), propolone B (11), propolone C (12), propolone D (13), sampsonione B (14), hyperisampsin E (15), and hyperisampsin F (16)], four xanthones [neriifolone C (17), 6-deoxyisojacareubin (18), osajaxanthone F (19), and brasilixanthone B (20)], two biphenyls [aucuparina (21) and 2,2-dimethyl-5-hydroxy-7-phenylchromene (22)], and two tocotrienol derivatives [2Z- and 2E-δ-tocotrienoloic acids (23 and 24)]. Compounds 1, 11, 12, 15, and 16 were isolated for the first time in the Clusiaceae family, compounds 17, 19 and 21 were isolated for the first time in the genus Clusia, whereas 2–10, 13, 14, 18, 20, 22–24 were isolated for the first time in Clusia criuva. Compounds 1, 2, 11, 12, 13 and 15 showed potent in vitro cytotoxic activity against GL-15 glioblastoma-derived human cell line. Chemophenetics significance of these compounds is described herein.     

Isolation of phenolic constituents and characterization of antioxidant markers from sunflower (Helianthus annuus) seed extract

A new compound, benzyl alcohol β-d-apiofuranosyl-(1→6)-β-d-(4-O-caffeoyl) glucopyranoside (1), was isolated from the seed of sunflower (Helianthus annuus), together with eight known phenolic compounds: caffeic acid (2), methyl caffeoate (3), chlorogenic acid (4), 4-O-caffeoylquinic acid (5), 3-O-caffeoylquinic acid (6), methyl chlorogenate (7), 3,5-di-O-caffeoylquinic acid (8), and eriodictyol 5-O-β-d-glucoside (9). Their structures were elucidated on the basis of spectroscopic methods and chemical evidence. The antioxidative effect of the phenolic constituents from the sunflower seeds was also evaluated based on the oxygen-radical absorbance capacity (ORAC), and the fraction containing caffeic acid derivatives showed a high antioxidant potency.     

Isolation of a second cryptic plasmid from Mycoplasma mycoides subsp. mycoides

Plasmids have rarely been detected in organisms constituting the genus Mycoplasma. Recently, the isolation of a cryptic plasmid from Mycoplasma mycoides subsp. mycoides has been described, and we report here the isolation of a second cryptic plasmid from this species. Restriction map and Southern blot analyses show that the second plasmid is distinct from the previously described plasmid, although a limited region of homology was detected. The availability of mycoplasmal cryptic plasmids may lead to the development of cloning vectors that replicate in these organisms.     

Isolation and characterization of nisin-producing Lactococcus lactis subsp. lactis from bean-sprouts

Bacterial isolates from bean-sprouts were screened for anti- Listeria monocytogenes bacteriocins using a well diffusion method. Thirty-four of 72 isolates inhibited the growth of L.monocytogenes Scott A. One, HPB 1688, which had the biggest inhibition zone against L.monocytogenes Scott A, was selected for subsequent analysis. Both ribotyping and DNAsequencing of 16S ribosomal RNA gene demonstrated that the isolate was Lactococcus lactis subsp. lactis . Polymerase chain reaction and nucleotide sequencing revealed that thegenomic DNA of the bean-sprout isolates contained a nisin Z structural gene. In MRS broth,bean-sprout isolate HPB 1688 survived at 3–4·5°C for at least 20 d, grew at 4°Cand produced anti-listerial compoundsat 5°C. When co-cultured with L. monocytogenes in MRS broth, the isolate inhibited thegrowth of L. monocytogenes at 4°C after 14d and at 10°C after 2 d. When co-inoculatedwith 10²cells g⁻¹ of L.monocytogenes on fresh-cut ready-to-eat Caesar salad, L. lactis subsp. lactis (10⁸cells g⁻¹) was able to reduce the number of L. monocytogenes by 1–1·4 logs after storage for 10 d at 7° and 10°C. A bacteriocin-producing Enterococcusfaecium was also able to reduce the numbers of L. monocytogenes onCaesar salad, butdid not act synergistically when co-inoculated with L. lactis subsp. lactis .     

Isolation and identification of new nisin-producing Lactococcus lactis subsp. lactis from milk

A method for isolating active nisin-producing strains of mesophilic lactococci was developed. Overall, 55 strains of mesophilic lactic acid bacteria were isolated from fresh cow’s milk obtained from milk farms in various regions throughout Russia; of them, 36 displayed nisin-synthesizing activity. The three most active strains were studied according to morphological, cultural, physiological, and biochemical characteristics and identified as Lactococcus lactis subsp. lactis. The species attribution of the strains studied was confirmed by the similarity of the nucleotide sequences of the 16S rRNA gene. The nucleotide sequences of the 16S rRNA genes were deposited with the GenBank under accession numbers DQ255951–DQ255954. The distinctions between these strains in physiological and biochemical characteristics and the ranges of their bactericide action on the microorganisms capable of developing in agricultural materials and food products were determined. The isolated strains displayed considerably wider ranges of action, which differed from the nisin-producing strain MGU and the commercial nisin preparation (Nisaplin), used as a biological preserving agent.     

Isolation and identification of new nisin-producing Lactococcus lactis subsp. lactis from milk

A method for isolating active nisin-producing strains of mesophilic lactococci was developed. Overall, 55 strains of mesophilic lactic acid bacteria were isolated from fresh cow's milk obtained from milk farms in various regions throughout Russia; of them, 36 displayed nisin-synthesizing activity. The three most active strains were studied according to morphological, cultural, physiological, and biochemical characteristics and identified as Lactococcus lactis subsp. lactis. The species attribution of the strains studied was confirmed by the similarity of the nucleotide sequences of the 16S rRNA gene. The nucleotide sequences of the 16S rRNA genes were deposited with the GenBank under accession numbers DQ255951-DQ255954. The distinctions between these strains in physiological and biochemical characteristics and the ranges of their bactericide action on the microorganisms capable of developing in agricultural materials and food products were determined. The isolated strains displayed considerably wider ranges of action, which differed from the nisin-producing strain MGU and the commercial nisin preparation (Nisaplin), used as a biological preserving agent.     

Chemical constituents of the roots of Ormocarpum sennoides subsp. zanzibaricum

Phytochemical investigation of the roots of O. sennoides subsp. zanzibaricum Brenan & J.B. Gillett resulted in the isolation of three biflavonoids (trime-chamaejasmin, (+)- chamaejasmin, (+)-liquiritigeninyl-(I-3,II-3)-naringenin), one bi-4-phenyldihydrocoumarin (diphysin), one isoflavan (glabridin), one triterpenoid (3-O-acetyloleanoic acid) and a phytosterol (β-sitosterol). Compounds were identified by detailed MS, 1D and 2D NMR spectroscopic analyses. Their absolute configurations were elucidated based on ECD spectra. The previously undescribed trime-chamaejasmin represents a bis-epi-chamaejasmenin C diastereomer. The chemophenetic significance is discussed in detail. The results contribute to the phytochemical characterization of the genus Ormocarpum and suggest a close chemophenetic relationship with other genera within the subfamily Papilionoideae. Furthermore, this report provides baseline data for comparing the two infraspecific taxa of O. sennoides (Willd.) DC.     

番茄化学成分的分离与鉴定

采用机械破碎法和果胶酶酶解法,使成熟番茄果实细胞内含物充分释放,上清液经D-101大孔树脂富集吸附后,再经一系列柱色谱分离得到6个化合物,根据其理化性质和波谱分析,分别鉴定为:芦丁(1)、槲皮素(2)、木犀草素(3)、番茄皂苷A(4)、豆甾醇(5)、熊果酸(6)。其中,化合物1、2、3、5、6为首次从该植物中分离得到。     

Isolation and identification of chemical constituents from tomato

采用机械破碎法和果胶酶酶解法,使成熟番茄果实细胞内含物充分释放,上清液经D-101大孔树脂富集吸附后,再经一系列柱色谱分离得到6个化合物,根据其理化性质和波谱分析,分别鉴定为:芦丁(1)、槲皮素(2)、木犀草素(3)、番茄皂苷A(4)、豆甾醇(5)、熊果酸(6).其中,化合物1、2、3、5、6为首次从该植物中分离得到.     

Isolation of Endoglucanase Genes from Pseudomonas fluorescens subsp. cellulosa and a Pseudomonas sp

Endoglucanase genes from Pseudomonas fluorescens subsp. cellulosa and Pseudomonas sp. were cloned and characterized. DNA hybridization studies showed that these genes are homologous and that each species has one copy of the gene per genome. The DNA fragment from Pseudomonas sp. codes for, at most, a 23-kilodalton endoglucanase.     

Isolation of Lactococcus lactis subsp. cremoris from nature by colony hybridization with rRNA probes.

Lactococcus lactis subsp. cremoris is widely used in the manufacture of fermented milk products. Despite numerous attempts, efforts to isolate new strains by traditional plating and identification methods have not been successful. Previously, we described oligonucleotide probes for 16S rRNAs which could be used to discriminate L. lactis subsp. cremoris from related strains. These probes were used in colony hybridization experiments to screen large numbers of colonies obtained from enrichment cultures. A total of 170 strains of L. lactis were isolated from six milk samples, two colostrum samples, and one corn sample by using oligonucleotide probe 212RLa specific for the species L. lactis. Fifty-nine of these isolates also hybridized to L. lactis subsp. cremoris-specific probe 68RCa, and 26 of the strains which hybridized to the L. lactis subsp. cremoris-specific probe had the L. lactis subsp. cremoris phenotype.