David Chaimovitsh

Biosynthesis of estragole and methyl-eugenol in sweet basil (Ocimum basilicum L). Developmental and chemotypic association of allylphenol O-methyltransferase activities

Sweet basil (Ocimum basilicum L., Lamiaceae) is a common herb, used for culinary and medicinal purposes. The essential oils of different sweet basil chemotypes contain various proportions of the allyl phenol derivatives estragole (methyl chavicol), eugenol, and methyl eugenol, as well as the monoterpene alcohol linalool. To monitor the developmental regulation of estragole biosynthesis in sweet basil, an enzymatic assay for S-adenosyl-L-methionine (SAM):chavicol O-methyltransferase activity was developed. Young leaves display high levels of chavicol O-methyltransferase activity, but the activity was negligible in older leaves, indicating that the O-methylation of chavicol primarily occurs early during leaf development. The O-methyltransferase activities detected in different sweet basil genotypes differed in their substrate specificities towards the methyl acceptor substrate. In the high-estragole-containing chemotype R3, the O-methyltransferase activity was highly specific for chavicol, while eugenol was virtually not O-methylated. In contrast, chemotype 147/97, that contains equal levels of estragole and methyl eugenol, displayed O-methyltransferase activities that accepted both chavicol and eugenol as substrates, generating estragole and methyl eugenol, respectively. Chemotype SW that contains high levels of eugenol, but lacks both estragole and methyl eugenol, had apparently no allylphenol dependent O-methyltransferase activities. These results indicate the presence of at least two types of allylphenol-specific O-methyltransferase activities in sweet basil chemotypes, one highly specific for chavicol; and a different one that can accept eugenol as a substrate. The relative availability and substrate specificities of these O-methyltransferase activities biochemically rationalizes the variation in the composition of the essential oils of these chemotypes.

Intraspecific variation of Chiliadenus iphionoides essential oil in Israel.

Chiliadenus iphionoides (Asteraceae), a shrub endemic to the Mediterranean region and widespread throughout Israel, is used in the traditional eastern Mediterranean medicine. Although recent research confirmed its pharmacological potential, C. iphionoides essential oil has not been adequately characterized chemically. Essential‐oil samples were collected from representative wild populations throughout Israel and characterized by GC/MS analysis. Considerable interpopulation variation was found for the composition of the essential oils. Multivariate analysis showed a significant correlation between the chemical composition and the geographic location, with three main chemotypes identified.

Chemical and Morphological Diversity in Wild Populations of Mentha longifolia in Israel

Populations of Mentha longifolia, an endangered species in Israel, were tested for essential oil composition and conservational ability. In 2002–2003, 25 wild populations country‐wide were tested, indicating population divergence into two chemotypes. Chemotype A was characterized by high levels of menthone and pulegone, and chemotype B by high levels of piperitenone oxide and piperitone oxide. Chemotype A was more abundant (22 of 25 populations) than chemotype B (11 of 25 populations). However, a chemotype/population interaction was not recorded (Pu2009>u20090.05). In spring 2003, seven of the 25 wild populations were resampled, propagated, and cultivated at the Newe Yaar campus. Then, in 2004, the propagated plants were tested for essential oil composition. The propagated plants maintained the essential oil composition as well as the chemotype‐frequency distribution of the original wild population from which they were obtained. Since a chemotype/population interaction was not recorded, and the cultivated plants displayed the wild population essential oil composition, it can be concluded that i) the chemotype diversity is genetically based, and ii) the M. longifolia populations sampled can be horticulturally conserved.

Antioxidant activity and phenol content of plant germplasm originating in the Dead Sea area

The antioxidative properties of forty-seven plant samples originating from the Ein Gedi Botanical Garden were screened. Their antioxidative activity, determined by DPPH radical scavenging assay and expressed as chlorogenic acid equivalent, ranged from 0.3 to 88 mg/g DW. The total phenol content, determined by the Folin-Ciocalteu assay, ranged from 2-82 mg/g DW. A substantial correlation was found between the antioxidative activity and the total phenol content among species. Tamarix nilotica, Suaeda vera, Acacia raddiana, Lawsonia alba, and Grewia villosa contained the highest antioxidative properties. This work consists of the first screening of the antioxidative properties of indigenous plants from the Dead Sea area. The future introduction of these plants as agricultural crops may provide novel natural sources for antioxidants.

Agronomic and economic evaluation of Vetiver grass (Vetiveria zizanioides L.) as means for phytoremediation of diesel polluted soils in Israel

Soil pollution in Israel, due to diesel contamination, is a major concern, with gas stations, factories and refineries being the main polluters (>60%). Vetiver grass (Vetiveria zizanioides L.) is a perennial grass belonging to the Poaceae family, and is recognized world-wide for its potential as a plant with phytoremediation traits to contaminated soils. It is demonstrated here to decrease diesel contamination in field and court-yard trials. Chemical soil analysis indicated up to a 79% decrease (Pxa0<xa0.05) in diesel pollution of contaminated soil planted with Vetiver; and at high soil contamination levels of 10xa0L/m2, a significant (Pxa0<xa0.05) reduction of 96, 96 and 87% was recorded at soil depths of 0-20, 20-40 and 40-60xa0cm, respectively. Furthermore, in field plots contaminated with diesel and planted with Vetiver, weeds biomass recovered to non-polluted levels following 8 to 9 months of Vetiver treatment. An economic evaluation conducted based on the cost-benefit analysis (CBA) principles, utilizing the Net Present Value (NPV) compared phytoremediation to other currently used decontamination procedures. The economic comparison showed that phytoremediation cleanup costs are lower and more beneficial to society at large, primarily from an ecosystem services perspective. Combining the results of the agronomic examination with the economic valuation, this research pointed out that phytoremediation with Vetiver has a non-negligible potential, making it a good solution for cleansing diesel from soils on a state-wide scale in Israel and worthy of further research and development.