Di-And Tri-Hydroxylated Kaurane Derivatives From Microbial Transformation Of Ent-Kaur-16-En-19-Ol By Cephalosporium Aphidicola And Their Allelopathic Activity On Lactuca Sativa (Lettuce)

Diterpenoid Constituents of Psiadia punctulata and Evaluation of Their Antimicrobial Activity

Sixteen diterpenes (1-16), along with 10 previously described compounds, including four flavonoids and six diterpenes, were isolated from the aerial parts of Psiadia punctulata growing in Saudi Arabia. The diterpene structures were elucidated using NMR spectroscopy and mass spectrometry data. Furthermore, a DFT/NMR procedure was used to suggest the relative configuration of several compounds. The labdane-derived skeletons, namely, ent-atisane, ent-beyerene, ent-trachylobane, and ent-kaurene, were identified. The extracts, fractions, and pure compounds were then tested against Staphylococcus aureus, Streptococcus mutans, Treponema denticola, and Lactobacillus plantarum. One diterpenoid, namely, psiadin, showed an additive effect with the antiseptic chlorhexidine, with a fractional inhibitory concentration index of less than 1. Additionally, psiadin showed a prospective inhibition activity for bacterial efflux pumps.

Microbiological Hydroxylations with Cephalosporium Aphidicola

The factors that affect the balance between biosynthetically patterned and xenobiotic transformations by the fungus Cephalosporium aphidicola involving terpenoid and steroidal substrates are reviewed. The potential role of the latter in the context of biodegradation is discussed.

The remarkable structural diversity achieved in ent-Kaurane Diterpenes by fungal biotransformations

The use of biotransformations in organic chemistry is widespread, with highlights of interesting applications in the functionalization of natural products containing unactivated carbons, like the kaurane diterpenes. A number of compounds with kaurane skeletons can be isolated in large amounts from several plant species and a myriad of biological activities has been related to these compounds. Studies on structure versus activity have showed that, in most cases, in kaurane diterpenes, activity increases with the increase of functionalization. Since naturally occurring kaurane diterpenes usually have limited functional groups to be used as targets for semi-synthetic modifications, production of more polar derivatives from kaurane diterpenes have been achieved mostly through the use of fungal biotransformations. In this review, selected examples the wonderful chemical diversity produced by fungi in kaurane diterpenes is presented. This diversity includes mainly hydroxylation of nearly all carbon atoms of the kaurane molecule, many of them carried out stereoselectively, as well as ring rearrangements, among other chemical modifications. Sources of starting materials, general biotransformation protocols employed, fungi with most consistent regioselectivity towards kaurane skeleton, as well as biological activities associated with starting materials and products are also described.