Steroidsaponine mit mehr als einer Zuckerkette, V. Avenacosid B, ein zweites bisdesmosidisches Steroidsaponin aus Avena sativa

Abstract

Die Struktur von Avenacosid B wurde durch stufenweisen enzymatischen Abbau, durch Hydrolyse des permethylierten Glykosids und mit Hilfe der Massenspektrometrie bestimmt. Danach hat es den Aufbau eines 3‐O‐{[α‐L‐Rhamnopyranosyl‐(1→4)]‐[〈β‐D‐glucopyranosyl‐(1→3)〉‐β‐D‐glucopyranosyl‐(1→2)]‐β‐D‐glucopyranosyl}‐3β.26‐dihydroxy‐22.25‐epoxy‐(22S: 25S)‐Δ5‐furostene‐26‐β‐D‐glucopyranosid (5).

Compromised disease resistance in saponin-deficient plants

“…Whereas the avenacins are restricted to the roots of oat and are the only saponins present in this part of the plant, the leaves contain another family of saponins, the steroidal avenacosides, A and B (27,28). Both the triterpenoid avenacins and the steroidal avenacosides are predicted to be synthesized from squalene-2,3-epoxide (16), but their biosynthetic pathways diverge after this point.…”

“…The exception, mutant 9, contained normal levels of avenacoside A but reduced levels of avenacoside B. Mutants 9 and 1,139, which are in different complementation groups, both accumulate monodeglucosyl avenacin A-1. Because avenacoside B differs from avenacoside A only in having an additional D-glucosyl residue (27,28), it appears that mutant 9 is defective in the ability to glucosylate both avenacin A-1 and avenacoside A. The reduced avenacoside B levels had no obvious effect on the interactions of mutant 9 with the leaf-infecting Stagonospora spp.…”

Preformed Antimicrobial Compounds and Plant Defense against Fungal Attack.

“…The occurrence of avenacins and avenacosides is restricted primarily to the genus Avena, although avenacins also occur in the closely related species Arrhenatherum elafius (Turner, 1953;Crombie and Crombie, 1986). The distribution of the two types of saponin within the plant is mutually exclusive: the avenacins are located in the root (Goodwin and Pollock, 1954;Maizel et al, 1964), and the avenacosides are located in the leaves and shoots (Tschesche et al, 1969;Tschesche and Lauven, 1971). Within these tissues, the major avenacin, avenacin A-1, is restricted to the root epidermal cells (Osbourn et al, 1994), whereas the avenacosides are present at higher concentrations in the epidermis than in the rest of the leaf (Kesselmeier and Urban, 1983).…”

Analysis, Heat Stability and Physiological Effects of Saponins from Oats

“…Tschesche and Schmidt (1966) proposed a name for the saponins in oats -avenacosides. Later the structure was elucidated for two oat saponins, avenacoside A and B (Tschesche et al, 1969;Tschesche and Lauven, 1971), both of which are bisdesmosidic (Fig. 1).…”