Diosgenin Biosynthesis Regulation In Dioscorea Composita

Diosgenin, one of the most important C-27steroidal sapogenins, has been a starting material for the production of steroidal hormones for over seven decades. It represents the main raw material for commercial synthesis of sex drugs and corticosteroids such as cortisone, testosterone, and progesterone. Progesterone is important in birth control pills manufacturing. Recent studies also provided that diosgenin possesses various pharmaceutical properties, e.g. antiviral, antifungal and anticancer effects. Diosgenin inhibits melanogenesis by activating the phosphatidylinositol-3-kinase pathway, and also may be an effective inhibitor of hyperpigmentation, its safety and efficacy against skin aging at the time of climacteric has been demonstrated.Because of its importance in the pharmaceutical industry the demand in diosgenin in the world is permanently growing. Commercially source material for steroids is only few species belonging mainly to the genus Dioscorea and Solanm; cultivated in a few area throughout the world.Today most of the diosgenin production in the world is met from Dioscorea floribunda and Dioscorea composita, but the latest is preferred for commercially production because of the high purity of diosgenin extracted from its tubers. Diosgenin is accumulated in small amounts in plant tissues. Its amount varies among different plant species, and among different organs of the same plant; and depend also on the grow conditions of the plant.The present study initiated for improving diosgenin content in D. composita has been carried out in two phases. In thefirst phase, we used three elicitors; methyl dihydro jasmonate (MDJ), ethephon (ETH) and salicylic acid (SA) to treat in vitro cultured D. composita in vitro cultures, for improving diosgenin biosynthesis and trying to understand physiological mechanisms involved in enhancement of diosgenin production by elicitation. Elicitors are applied in different concentrations and at different times. Here, a part of diosgenin content, photosynthetic pigments, primary metabolites, enzymatic and non-enzymatic antioxidant activity were assayed.In samples treated with MDJ on D14(14days after subculture), diosgenin content has been increased at concentration20?M by69%ver that of control). D7Ethephon treatment at low concentrations considerably increased diosgenin level, reaching the highest content at40mg/L up to140%ver the level in control plants; whereas salicylic acid applied on D7and at concentration100uM gave the most significant level of diosgenin (150%ver that of control).We determined the chlorophylls and carotenoids content of explants; and observed that elicitors have no considerable effect on these parameters apart of some concentration dependent slight decrease. Soluble proteins content in treated samples decreased progressively96hours after elicitors' pplication (24h for SA treatment). It has been observed that lipid peroxidation (MDA) and hydrogen peroxide (H2O2) level begin to increase when protein decrease.Antioxidant enzymes activities have been determined in the treated and control samples.In the second phase, we investigated the effect of same three elicitors (MDJ, ETH, and SA) on diosgenin level in the tubers of two years old wild growing D. composita. Different concentrations of elicitors have been sprayed on to individual isolated plant, three times with four months intervals.All the elicitors at different levels induced increase in diosgenin content of treated plantlets compared to control plants on the basis of dry weight.Methyl dihydro jasmonate (MDJ) at concentration60?l/L increased diosgenin content by41.77%; ethephon at concentration lml/L induced increase up to45.78%; and salicylic acid, by59.67%at concentration50mg/LDynamic changes of diosgenin content in different organs of D. composite showed that diosgenin in the tubers is3to5folds and5to7folds higher than that in the stems and leaves respectively.