ent-Atisane diterpenoids: isolation, structure and bioactivity

Covering: up to 2020 ent-Atisane diterpenoids are a class of over 150 members with diverse structures and valuable bioactivities. These compounds share a curious history in which the synthesis of the archetypal member preceded its isolation from natural sources. In this review, we provide a comprehensive summary of the isolation, structure, and bioactivity of ent-atisane diterpenoids from their discovery in 1965 to the present day.

Identification of catechin as one of the flavonoids from Combretum albiflorum bark extract that reduces the production of quorum-sensing-controlled virulence factors in Pseudomonas aeruginosa PAO1

Quorum-sensing (QS) regulates the production of key virulence factors in Pseudomonas aeruginosa and other important pathogenic bacteria. In this report, extracts of leaves and bark of Combretum albiflorum (Tul.) Jongkind (Combretaceae) were found to quench the production of QS-dependent factors in P. aeruginosa PAO1. Chromatographic fractionation of the crude active extract generated several active fractions containing flavonoids, as shown by their typical spectral features. Purification and structural characterization of one of the active compounds led to the identification of the flavan-3-ol catechin [(2R,3S)-2-(3,4-dihydroxyphenyl)-3,4-dihydro-1(2H)-benzopyran-3,5,7-triol]. The identity of catechin as one of the active molecules was confirmed by comparing the high-pressure liquid chromatography profiles and the mass spectrometry spectra obtained for a catechin standard and for the active C. albiflorum fraction. Moreover, standard catechin had a significant negative effect on pyocyanin and elastase productions and biofilm formation, as well as on the expression of the QS-regulated genes lasB and rhlA and of the key QS regulatory genes lasI, lasR, rhlI, and rhlR. The use of RhlR- and LasR-based biosensors indicated that catechin might interfere with the perception of the QS signal N-butanoyl-l-homoserine lactone by RhlR, thereby leading to a reduction of the production of QS factors. Hence, catechin, along with other flavonoids produced by higher plants, might constitute a first line of defense against pathogenic attacks by affecting QS mechanisms and thereby virulence factor production.

Diterpenoids

This review covers the isolation and structures of diterpenoids, including labdanes, clerodanes,pimaranes, abietanes, kauranes, cembranolides, taxanes and marine diterpenoids. The literature from January to December 2005 is reviewed, and 195 references are cited.