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Altogether, 110 species of the genus Stevia, comprising both herbarium and fresh leaf samples, were screened for the presence of sweet ent-kaurene glycosides, using a combination of tlc and hplc, followed by gc/ms. Stevioside and rebaudiosides A and C were detected in a Stevia rebaudiana herbarium specimen collected in Paraguay in 1919, and stevioside was observed as a constituent of a Stevia phlebophylla herbarium specimen collected in Mexico in 1889. Steviol glycosides were not detected in any of the other 108 Stevia species studied. The phytochemical results obtained in this study are correlated with those of preliminary organoleptic tests on the sweetness of these Stevia samples, and the chemotaxonomic implications of the present findings are discussed.

Bioactivity-directed fractionation, using brine shrimp lethality and murine hypoglycemia, of an ethanol extract prepared from Tillandsia usneoides, led to the isolation of four apparently bioactive compounds from the water-soluble fraction. The compounds were identified as citric acid, succinic acid, 3-hydroxy-3-methylglutaric acid (HMG), and 3,6,3',5'-tetramethoxy-5,7,4'-trihydroxyflavone-7-O-beta-D-g lucoside. The brine shrimp lethality of the acids was simply due to acidity; however, HMG elicited significant hypoglycemic responses in fasting normal mice. Ethyl and methyl esters of citric acid were prepared and tested in the murine hypoglycemic assay. Five of the predominant sugars were identified by tlc. Free thymidine was also isolated. Further evaluation of HMG and other potential inhibitors of HMG CoA lyase, in the treatment of symptoms of diabetes mellitus, is suggested.

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