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Abstract

A total of 184 Stevia leaf samples taken from herbarium specimens, representing 110 species and 121 taxa, were screened organoleptically for their taste sensation. Fragments of a 62-year-old leaf of S. rebaudiana exhibited a potent and prolonged sensation of sweetness, thereby indicating the stability of its sweet ent-kaurene glycoside constituents to drying, preservation, mounting and storage. No other leaf samples exhibited an intensity of sweetness equivalent to that of S. rebaudiana, though 18 species and varieties were considered to exhibit a sweet taste. These taxa appear to be promising candidates for future phytochemical investigation for new and known ent-kaurene glycosides.

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Sixty species of the genus Euphorbia were tested for skin inflammation effects, as their crude latex or herb extracts, using the mice ear test. The production of skin inflammation is a general property o f the extracts examined, only seven of the species failing to produce redness of mice ears. For the crude extracts producing inflammation of the skin their potency varied from about 0.2 to 45 pgl.5 pl of acetone extract. The inflammation produced by the majority of plant extracts reached a maximum effect after 24 hours, but several species demonstrated short term irritant effects reaching a maximum activity 4 hours after application to the skin, their effects thereafter decreasing in an approximately log. linear manner with time. Examples of this type of biological effect were found in the Sections Tithymalus and Euphorbium of the classification of the genus proposed by PAX and HOFFMANN. Non-irritant extracts were obtained mainly from the Sections Poinsettia and AnisophylIum. lntroductionThe genus Euphorbia comprises a large and diverse group of plants which are characterised by the presence of a white milkly latex (HECKER, 1968). Ethnobotanical records (WATT and BREYER-BRANDWIJK, 1962) indicate that the toxicological dangers represented by this genus have long been recognised as far as the large succulent species are concerned. The principal hazard is the extremely severe skin inflammation response on external application of the latex which lasts for up to 24 hours. In 'tropical regions such lesions on livestock are susceptible to secondary infection , and mucous membranes including the eyes are particularly affected. The dried plant material and latex (Euphorbium) is sternutatory. Medicinal uses of these plants included treatments for skin diseases, gonorrhea, migraine, intestinal parasites and wart cures. The plant latex has been used as fish poison, insecticide and an ordeal poison. Because of the medicinal interest in this group of plants, they have been the subject of intense phytochemical examination and groups of compounds isolated @ Hippokrates Vcrlag GmbH. Stuctgart 1975

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Five ingenane derivatives, 3-O-n-(deca-2,4,6-trienoyl)-16-O-[(Z)-2-methyl-2-butenoyl]-16-hydroxyingenol (1), 3-O-[(Z)-2-methyl-2-butenoyl]-5,16,20-O-triacetyl-16-hydroxyingenol (2), 3-O-[(Z)-2-methyl-2-butenoyl]-16,20-O-diacetyl-16-hydroxyingenol (3), 3-O-[(Z)-2-methyl-2-butenoyl]-20-O-acetylingenol (4), and 3-O-[(Z)-2-methyl-2-butenoyl]-16-O-acetyl-20-deoxy-16-hydroxyingenol (5) were isolated with a new procedure that uses droplet counter-current chromatography, from a dermatitis-producing fraction of the latex of Euphorbia hermentiana Lem. The structures of the new compounds 2,3, and 5 were established by the interpretation of their spectroscopic data and those of their hydrolytic and acetylated derivatives.

: ince reactive oxygen radicals play an important role in carcinogenesis and other human disease states, antioxidants present in consumable fruits, vegetables, and beverages have received considerable attention as cancer chemopreventive agents. Thus, in order to identify antioxidants in plant extracts, test materials were assessed for potential to scavenge stable 1,2-diphenyl-2-picrylhydrazyl (DPPH) free radicals, reduce TPA-induced free radical formation in cultured HL-60 human leukemia cells, and inhibit responses observed with a xanthine/xanthine oxidase assay system. Approximately 700 plant extracts were evaluated, and 28 were found to be active in the DPPH free radical scavenging assay. Based on secondary analyses performed to assess inhibition of 7,12-dimethylbenz(a)anthracene-induced preneoplastic lesion formation with a mouse mammary organ culture model, Chorizanthe diffusa Benth. (Polygonaceae), Mezoneuron cucullatum Roxb. (Leguminosae), Cerbera manghas L. (Apocynaceae) and Daphniphyllum calycinum Benth. (Daphniphyllaceae) were selected and subjected to bioassay-guided fractionation. 5,7,3',5'-Tetrahydroxy-8,4'-dimethoxyflavonol, 5,8,4'-trihydroxy-7,3'-dimethoxyflavonol, 5,3',4'-trihydroxy-7-methoxyflavonol, and 6,3',4'-trihydroxy-7-methoxyflavonol were identified as active principles from C. diffusa. Piceatannol, trans-resveratrol, apigenin and scirpusin A were found as the active principles of M. cucullatum, olivil, (-)-carinol, and (+)-cycloolivil were active principles from C. manghas, and 5,6,7,4'-tetrahydroxyflavone 3-O-rutinoside and kaempferol 3-O-neohesperidoside were active principles from D. calycinum. Of these substances, the hydroxystilbenes piceatannol and transresveratrol have thus far been shown to inhibit carcinogen-induced preneoplastic lesion formation in the mouse mammary gland organ culture model.