1,721,082 research outputs found
Chemistry and biological activity of triterpene saponins from Medicago species
No full textNaturally occurring saponins are a large group of triterpene and steroid glycosides characterized by several biological and pharmacological properties. The Medicago genus represents a valuable source of saponins which have been extensively investigated. This review Summarizes the chemical features of saponins from Medicago species and their biological activity, with particular attention to their antimicrobial, insecticidal, allelopathic and cytotoxic effects. Influence of saponins on animal metabolism is also reported
Un salto, un perchè
No full textIl testo presenta due laboratori su attività di movimento e un inquadramento teorico sui principali modelli di psicomotricità adottati nelle scuole dell'infanzia. Attraverso la presentazione di giochi con il corpo e vari materiali, si approfondiscono aspetti emotivi, espressivi e funzionali del gioco dei bambini, differenziando gioco senso motorio e simbolico. Si indaga il significato di azioni quali il saltare, il nascondersi, il fare case e strade, e si presenta lo sviluppo degli schemi motori di base
Biosynthesis of saponins in the genus Medicago
No full textSaponins from Medicago species are glycosidic compounds with an aglycone moiety formed through the enzymatic cyclization of 2,3-oxidosqualene by the beta-amyrin cyclase. All the saponins from Medicago genus possess the triterpenic pentacyclic nucleus belonging to the class of beta-amyrin. The so formed beta-amyrin skeleton can be further modified by oxidative reactions, mediated by cytochromes belonging to the class of cytochrome P450, to give different saponin compounds, characterized by the presence of hydroxyl or carboxyl groups located in specific positions of the triterpenic skeleton. Based on the position and the oxidation degree of the substituents, it is possible to distinguish two groups of saponins (sapogenins) in Medicago spp: (1) sapogenins possessing an OH group on C-24 (soyasapogenols A, B and E) without any substituent at the C-28 atom, and (2) sapogenins possessing the COOH group at C-28 that are associated with different oxidation degrees (zero, OH, CHO, COOH) at C-23. These results seem to indicate that the oxidation at C-24 and the presence of the COOH group at C-28 are mutually exclusive. The subdivision in the aglycone moiety is reflected also in the sugar moiety, operated by glycosyltranferases, as the saponins of the two groups differ for the position and the nature of the sugar chains. Based on these findings, new considerations on the biosynthesis of saponins in the genus Medicago can be drawn and a biosynthetic scheme is proposed
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