The study was conducted to evaluate the effect of salinity by two salts (NaCl and CuSO4), yeast extract and drought on content and constituents of silymarin in the seeds of cultivated Silybum marianum in the green house to the fruiting growth stage. The used NaCl treatment increased the number of Inflorescences per plant, weight of seeds per each Inflorescence and total weight of seeds per plant. The other treatments reduced these seed parameters especially drought which caused their reductions by 53.3, 52.1, and 77.6% compared to control respectively. The significant polynomial regression equation between number of Inflorescences and seed weight showed that production of more than 3 Inflorescences per plant decreased the weight of seed of Inflorescences. All of the used treatments except yeast extract increased seed silymarin content with a highest value by NaCl. The total silymarin produced per plant was high by NaCl followed by Cu SO4 while by yeast extract and drought it was low compared to the control as it was mainly a function of the effect on the plant seed weight. The HPLC analysis of silymarin revealed the presence of all important silymarin constituents (silychristin, silydianin, silybin A, silybin B, isosilybin A&B), and silydianin represented the major component under all treatments. Drought and yeast extract mostly decreased all silymarin constituents while NaCl and Cu SO4 increased them except silybin A which decreased by all treatment compared to the control. Silymarin efficiency was high under drought stress in comparison with the other treatments due to acquiring high content of the medicinally important silybin constituents. The study suggests cultivation of Silybum marianum in newly reclaimed desert area and slightly saline area as an important plant for the production silymarin.
Key words: Silybum marianum, silymarin, Silychristin, Silydianin, Silybin A, Silybin B, Isosilybin A&B, drought, yeast extract, salinity by NaCl and CuSO4
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