Quantification of Diosgenin content in Dioscorea bulbifera linn germplasm from Uganda

Abstract

Diosgenin is mainly found in wild Dioscorea sp. and is a well-known precursor of steroidal and contraceptive drugs. However, due to large market demand and increase in ecological damage, available wild Dioscorea spp. specifically Dioscorea bulbifera is gradually declining. This study therefore quantified the amounts of Diosgenin in D. bulbifera accessions in Uganda for conservation of high yielding germplasm. Mature aerial bulbs of D. bulbifera were collected from various regions of Uganda, that is; the Eastern (Mt Elgon forest reserve), Northern (Abur-buru forest reserve), Western (Kasyoha Kitomi forest reserve and Bugoma central forest reserve), Southwestern (Bwindi Impenetrable forest) and Central (Mabira central forest reserve). Samples were separately washed, shredded into small pieces and lyophilised. The freeze-dried samples were powdered mechanically and kept in polythene bags for extraction. The powdered samples were macerated with 70% ethanol, concentrated in vacuo to dryness. The extracts were reconstituted with water and defatted with hexane in a separating flask before they were partitioned with n-butanol. The butanol layers were concentrated and analyzed using High Performance Liquid Chromatography (HPLC) and also qualitative phytochemistry was done on the crude extracts. Results obtained from HPLC showed the highest concentration of diosgenin in Mabira forest reserve population with 0.996a mg/g, while Bwindi impenetrable forest population and Mt. Elgon populations had significantly lower concentration of 0.36e and 0.373e mg/g respectively at a retention time of 2.803 min. The method employed in current study confirmed a significant variation in the diosgenin concentration in Ugandan D. bulbifera populations except for germplasm from Bwindi and Elgon. The Diosgenin quantities were highest in Mabira central forest reserve with 0.996a mg/g implying the germplasm from Mabira would be ideal for conservation