Augustin E. Nkengfack

Prenylated isoflavanone from Erythrina eriotricha

Bioassay-directed fractionation of a methylene chloride extract of the root bark of Erythrina eriotricha resulted in the isolation of a novel isoflavanone, named eriotrichin B, and the five known pterocarpans, isonorautenol, erybraedin A, erybraedin C, erybraedin D and erybraedin E. The structure of the new compound has been investigated by extensive spectroscopic studies, including 2D NMR and chemical evidence. The in vitro antimicrobial spectrum and potencies of the isolated compounds are also reported.

Phenolic metabolites from Erythrina species

From the stem and root bark of Erythrina sigmoidea and E. eriotricha, one new prenylated flavanone, named sigmoidin L, and two new esters of ferulic and isoferulic acid, erythrinassinates C and D, were isolated together with eight known compounds, including one ester of isoferulic acid [3β-O-(E)-isoferuloyl oleanolic acid], one flavanone (sigmoidin A), four isoflavones (scandenone, 6,8-diprenylgenistein), flemiphilippinin B and 8-prenyldaidzein and two pterocarpans (gangetinin and calopocarpin). Their structures were elucidated by analysis of spectral data and chemical evidence. The in vitro anitmicrobial spectrum and potencies of the isolated compounds are also reported.

Scaphopetalone and scaphopetalumate, a lignan and a triterpene ester from Scaphopetalum thonneri.

From the methanol extract of the stem bark of Scaphopetalum thonneri, two new compounds, including one lignan, named scaphopetalone, one new ester of ferulic acid, named scaphopetalumate were isolated together with three known compounds including: two coumarins (scopoletin and scopolin), and one pentacyclic triterpene (oleanolic acid). The structure of the new compounds were elucidated by means of spectroscopic analyses.

Furanoflavones from root bark of Millettia sanagana

Abstract A new furanoflavone, named sanaganone, was isolated from the root bark of Millettia sanagana in addition to four known compounds, pongamol, lanceolatin B, kanjone and 5-methoxy furano [7,8:4″,5″] flavone. The structure of the new compound was elucidated by spectroscopic analysis, including 2D NMR techniques (DQF COSY, HETCOR, long-range HETCOR and NOESY), as 2‴,2‴-dimethylpyrano [5,6:5‴,6‴] furano [7,8:4″,5″] flavone.

Further flavonoids from Erythrina species

Abstract A new dihydroflavonol, eriotrinol, and a new prenylated flavanone, sigmoidin G, have been isolated from the stem bark of Erythrina eriotricha and E. sigmoidea, respectively. Their structures were established as (2R,3R)-5,4′-dihydroxy-3′-methoxy-6″,6″-dimethylpyrano [2″,3″ : 7,6] dihydroflavonol and 5,7,5′,4″,5″-pentahydroxy-6″,6″-di-methylpyrano [2″,3″4:3′,4′] flavanone on the basis of spectroscopic means and chemical evidence. The previous known 4′-O- methylalpinumisoflavone, sigmoidin B and pentacyclic triterpene, erythrodiol, have been also isolated.

Conrauinones C and D, two isoflavones from stem bark of Millettia conraui☆

Abstract Analysis of the stem bark of Millettia conraui led to the isolation of two new O -geranylated isoflavones named conrauinones C and D together with the known 7-hydroxy-6-methoxy-3′,4′-methylenedioxyisoflavone. The structure elucidation of the two new compounds by spectroscopic studies is described.

Diterpenoid and limonoids from the stem of Pterorhachis zenkeri

One new diterpenoid, methyl 3alpha-hydroxy-7-oxo-dehydroabietate (1), two new limonoids, 3alpha-deacetyl-amoorastatin (2) and 9beta-amoorastatin (3), and the known limonoid amoorastatin (4) were isolated from the stem of Pterorhachis zenkeri.

Antrocarines A-F, antiplasmodial ergostane steroids from the stem bark of Antrocaryon klaineanum.

During a study on the chemistry and biological activity of Antrocaryon klaineanum Pierre, six new sterols including 4,24(28)-ergostadiene-6α,7α-diol (1), 6α-methoxy-4,24(28)-ergostadiene-7α,20S-diol (2), 6α-methoxy-4,24(28)-ergostadien-7α-ol (3), 20S-hydroxy-24(28)-ergosten-3-one (4), 7α-hydroxy-4,24(28)-ergostadien-3-one (5), and 24(28)-ergostene-3β,6α-diol (6) were characterized by physical and spectroscopic means. The known steroids 7 and 8 were also isolated. The crude extract and the isolated compounds were evaluated for their ability to inhibit the 3D7 strain of Plasmodium falciparum. Compounds 2, 3, and 8 showed potent activity while that of the crude extract was moderate.