[Lignans with inhibitory effect on 5α-reductase from Urtica cannabina].

The lignans in Urtica cannabina were isolated by preparative HPLC, silica, and ODS column chromatographies, and identified by NMR and HR-MS. The inhibitory activities on 5α-reductase were evaluated in vitro. As a result, ten secolignans,(2R,4S)-2,4-bis(3-methoxyl-4-hydroxyphenyl)-3-butoxypropanol(1), 3,4-trans-3-hydroxymethyl-4-[bis(3,4-dimethoxyphenyl)methyl] butyrolactone(2), 3,4-trans-3-hydroxymethyl-4-[(3,4-dimethoxyphenyl)(3-methoxyl-4-hydroxyphenyl)methyl] butyrolactone(3), 3,4-trans-3-hydroxymethyl-4-[bis(3-methoxyl-4-hydroxyphenyl)methyl] butyrolactone(trans urticol, 4), 3,4-trans-3-hydroxymethyl-4-[bis(3,4-dimethoxyphenyl)methyl] butyrolactone-3-O-ß-D-glucopyranoside(5), 3,4-trans-3-hydroxymethyl-4-[(3,4-dimethoxyphenyl)(3-methoxyl-4-hydroxyphenyl)methyl]butyrolactone-3-O-ß-D-glucopyranoside(6), 3,4-trans-3-hydroxymethyl-4-[bis(3-methoxyl-4-hydroxyphenyl)methyl]butyrolactone-3-O-ß-D-glucopyranoside(trans-urticol-7-O-ß-D-glucopyranoside, 7), cycloolivil-4-O-ß-D-glucopyranoside(8), isolariciresinol-4'-O-ß-D-glucopyranoside(9), and olivil-4'-O-ß-D-glucopyranoside(10), together with a polyphenol [α-viniferin(11)], were isolated from U. cannabina for the first time. Compound 1 was a new lignan. Compound 7 was potent in inhibiting 5α-reductase.

Cadmium-induced oxidative stress and response of the ascorbate-glutathione cycle in Bechmeria nivea (L.) Gaud.

Bechmeria nivea (L.) Gaud. (ramie) seedlings subjected to a series of cadmium (Cd) concentrations (0, 1, 3 and 7 mg l(-1)) over a 10d period were investigated with regard to the uptake and distribution of Cd, its effect on membrane lipid and chlorophyll synthesis, and response of the ascorbate-glutathione cycle in both leaves and roots. Increased Cd level in the medium resulted in a significant enhancement of Cd concentration in tested plants, with most accumulation in roots. Ramie under Cd stress exhibited increased level of lipid peroxidation, as was evidenced by the increased malondialdehyde content (MDA, an index of lipid peroxidation) in leaves and roots. Shorter exposure to lower Cd concentrations (1 and 3 mg l(-1)) led to a stimulation of chlorophyll synthesis, while longer exposure and higher Cd concentration (7 mg l(-1)) led to a remarkable breakdown of chlorophyll, suggesting that Cd caused oxidative stress in ramie. The antioxidant system as represented by the ascorbate-glutathione pathway was clearly activated following Cd exposure. An overall increase in the metabolite levels and major constituting enzyme activities (ascorbate peroxidase APX and glutathione reductase GR) was observed in ramie treated with 1 and 3 mg l(-1) Cd throughout the entire experimental period, while prolongation of exposure to 7 mg l(-1) Cd resulted in decrease of GR activity and GSH pool in roots which may limit the operation of the whole cycle. Results suggest that Cd-induced oxidative damage in ramie is closely associated with the efficiency of its intrinsic antioxidant mechanisms and the accelerated operation of ascorbate-glutathione cycle provides ramie with enhanced Cd-stress tolerance.

[Phytotoxic effect of soil cadmium pollution on ramie].

A microplot locating experiment was conducted to study the phytotoxic effect of adding Cd in soil on ramie plants. The results showed that the contents of chlorophyll a and b of leaf, and the photosynthesis productivity of ramie plant were significant reduced by the addition of Cd. As the content of soil Cd reached to 14 mg.kg-1, the biomass yield of the above-ground part of ramie plants was 20% lower than the control, and was 50% lower when soil Cd content was at 100 mg.kg-1. The number of effective tillers was a main factor affecting the yield of ramie raw fibers, and Cd addition had a relatively small effect on the quality of raime fibers. It is suggested that a synthetical technology of soil treatment and agronomic measures should be applied to eliminate the toxic effect of soil Cd and to enhance the resistance of plant against soil Cd pollution when employing ramie as the alternative of food and vegetable crops in a Cd-polluted region, which is also important for a higher yield of ramie.