title: Structure-biological activity relationships in triterpenic saponins: the relative activity of protobassic acid and its derivatives against plant pathogenic fungi.
abstract: BACKGROUND
  Triterpenic saponins from Sapindus mukorossi Gaertn. and Diploknema butyracea JF Gmelin were evaluated for in vitro antifungal activity against four phytopathogenic fungi. The study of the structure-antifungal activity relationships of protobassic acid saponins was widened by including semi-synthetic derivatives.
  
  
  RESULTS
  Diploknema butyracea saponins exhibited significant antifungal activity against three fungi (ED(50) 230-455 microg mL(-1)), whereas S. mukorossi saponin was effective against two fungi (ED(50) 181-407 microg mL(-1)). The n-butanol extract after preparative HPLC separation provided two saponins from D. butyracea saponin mixture: 3-O-[beta-D-glucopyarnosyl-beta-D-glucopyranosyl]-16-alpha-hydroxyprotobassic acid-28-O-[arabinopyranosyl-glucopyranosyl-xylopyranosyl]-arabinopyranoside (MI-I), and 3-O-beta-D-glucopyranosyl-glucopyranosyl-glucopyranosyl-16-alpha-hydroxyprotobassic acid-28-O-[arabinopyranosyl-xylopyranosyl-arabinopyranosyl]-apiofuranoside (MI-III). The single saponin extracted from S. mukorossi saponin mixture was identified as 3-O-[O-acetyl-beta-D-xylopyranosyl-beta-D-arabinopyranosyl-beta-D-rhamnopyranosyl] hederagenin-28-O[beta-D-glucopyranosyl-beta-D-glucopyranosyl-beta-D-rhamnopyranosyl] ester (SM-I). Monodesmosides resulting from the partial degradation of hederagenin and hydroxyprotobassic acid bisdesmosides exhibited significant reduction in antifungal effect. Further removal of sugar moiety yielded complete loss in activity. The antifungal activity of the triterpenic saponins was associated with their aglycone moieties, and esterification of the hydroxyl group led to change in antifungal activity.
  
  
  CONCLUSIONS
  Sapindus mukorossi saponin, which is effective against Rhizoctonia bataticola (Taub.) Briton Jones and Sclerotium rolfsii Sacc., can be exploited for the development of a natural fungicide. A sugar moiety is a prerequisite for the antifungal activity of triterpenic saponin.
authors.affiliation: Division of Agricultural Chemicals, I.A.R.I, New Delhi, India. s_supradip@yahoo.com
authors.forename: Supradip
authors.initials: S
authors.lastname: Saha
authors.forename: Suresh
authors.initials: S
authors.lastname: Walia
authors.forename: Jitendra
authors.initials: J
authors.lastname: Kumar
authors.forename: Balraj S
authors.initials: BS
authors.lastname: Parmar
mesh_terms: D000935:Antifungal Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D005658:Fungi / Q000187:drug effects*; D010944:Plants / Q000382:microbiology*; D032127:Sapindus / Q000737:chemistry; D012503:Saponins / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D029632:Sapotaceae / Q000737:chemistry; D013329:Structure-Activity Relationship; D014315:Triterpenes / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*
chemical_list: D000935:Antifungal Agents; D012503:Saponins; D014315:Triterpenes; C485321:protobassic acid