Quality assessment of tulbaghia bulbs

Bulbs of Tulbaghia species (Alliaceae) are used in traditional medicine in Southern Africa for anti-fungal purposes due to their content of sulfur-containing compounds. The main compound is marasmin which is enzymatical converted to marasmecin, which undergoes further chemical degradation. A number of species, T. acutiloba, T. alliacea, T. cominsii, T. galpinii, T. montana, T. natalensis, T. simmlerii and T. violacea, were included in the study. Crushing of fresh bulb material with liquid nitrogen followed by extraction with ethanol yielded good extraction of the sulfur compounds. Sulfur compounds were evaluated by TLC on silica plates eluted with toluene:ethyl acetate 10:3, detected with palladium-II-chloride. All species contained the same sulfur compounds, but in varying concentrations, except T. simmelerii, which had very low levels of sulfur compounds. A simple, quantitative TLC dilution method was developed. Extracts were applied in decreasing amounts until the main sulfur compound at R_f 0.5 no longer was visible. Setting the minimum detection limit to 1µl of test extract, three of the species tested, T. alliaceae, T. violaceae and T. galpinii would be included in the drug Tulbaghia bulbus. Possible adulterants could be Allium sativa and Agapanthus campanulatus. A. sativa contains sulfur compounds indistinguishable from those in Tulbaghia. A. campanulatus does not contain sulfur compounds, and the ethanol extract has characteristic bands on TLC when treated with anisaldehyde-R, which allows detection of adulteration with 10% A. campanulatus.