Biotransformation of an africanane sesquiterpene by the fungus Mucor plumbeus

Insect Antifeedant Benzofurans from Pericallis Species

In this work, we have studied the benzofurans of Pericallis echinata (aerial parts and transformed roots), P. steetzii (aerial parts and transformed roots), P. lanata (aerial parts), and P. murrayi (aerial parts and roots). This work has permitted the isolation of the new benzofurans 10-ethoxy-11-hydroxy-10,11-dihydroeuparin (10), (-)-eupachinin A ethyl ether (12), 11,15-didehydro-eupachinin A (13), 10,12-dihydroxy-11-angelyloxy-10,11-dihydroeuparin (14), 2,4-dihydroxy-5-formyl-acetophenone (15) isolated for the first time as a natural product, 11-angelyloxy-10,11-dihydroeuparin (16), and 12-angelyloxyeuparone (17), along with several known ones (1-9, 11). In addition, the incubation of the abundant component, 6-hydroxytremetone (1), with the fungus Mucor plumbeus has been studied. Benzofurans in the tremetone series (1, 1a, 2-5, 18, 18a), the euparin series (6, 7, 7a, 8-10, 14, 16), and the eupachinin-type (11, 12) were tested for antifeedant effects against the insect Spodoptera littoralis. The antifeedant compounds (1, 4, 6, 11, 12) were further tested for postingestive effects on S. littoralis larvae. The most antifeedant compounds were among the tremetone series, with 3-ethoxy-hydroxy-tremetone (4) being the strongest antifeedant. Glucosylation of 1 by its biotransformation with Mucor plumbeus gave inactive products. Among the euparin series, the dihydroxyangelate 14 was the most active, followed by euparin (6). The eupachinin-type compounds (11, 12) were both antifeedants. Compounds 4, 11, and 12 showed antifeedant effects without postingestive toxicity to orally dosed S. littoralis larvae. Euparin (6) had postingestive toxicity that was enhanced by the synergist piperonyl butoxide.

Biotransformation of sesquiterpenoids: a recent insight

Sesquiterpenoids have been identified as natural compounds showing remarkable biological activities found in medicinal plants. There is great interest in developing methods to obtain sesquiterpenoids derivatives and biotransformation is one of the alternative methods for structural modification of complex sesquiterpenes structures. Biotransformation is a great drug design tool offering high selectivity and green method. The present review describes a comprehensive summary of biotransformation products of sesquiterpenoids and its structural modification utilizing a variety of biocatalysts including microorganisms, plant tissue culture and enzymes. This review covers recent literatures from 2007 until 2020 and highlights the experimental conditions for each biotransformation process.

Scalable Syntheses and Biological Evaluation of Africane-type Sesquiterpenoids

Practical total syntheses of africane-type sesquiterpenoids were realized by reexamination of a divergent strategy employing optimized three-component coupling followed by ring-closing metathesis and substrate-controlled cyclopropanation. This sequential eight-step conversion provided Δ9(15)-africanene, a common bicyclo[5.3.0]decane intermediate for the syntheses of africane derivatives, in more than twice the yield as in the previous approach. The scalability and robustness of this improved synthetic route were confirmed by gram-scale preparation of Δ9(15)-africanene. In vitro cell-based assays of the synthesized africane-type sesquiterpenoids disclosed that ester-incorporating derivatives showed cytotoxic activity against HeLa cells. The effect of relative and absolute stereochemistry of africane-9,15-diol monoacetates on the cytotoxicity against HeLa cells was also investigated.

Sesquiterpene Lactones from Artemisia absinthium. Biotransformation and Rearrangement of the Insect Antifeedant 3α-hydroxypelenolide

Three new compounds, the sesquiterpenes absilactone and hansonlactone and the acetophenone derivative ajenjol, have been isolated from a cultivated variety of Artemisia absinthium. In addition, the major lactone isolated, 3α-hydroxypelenolide, was biotransformed by the fungus Mucor plumbeus affording the corresponding 1β, 10α-epoxide. A cadinane derivative was formed by an acid rearrangement produced in the culture medium, but not by the enzymatic system of the fungus. Furthermore, 3α-hydroxypelenolide showed strong antifeedant effects against Leptinotarsa decemlineata and cytotoxic activity to Sf9 insect cells, while the biotransformed compounds showed antifeedant postingestive effects against Spodoptera littoralis.