Biotransformation of ent-pimaradienoic acid by cell cultures of Aspergillus niger

Abstract

Microbial transformation stands out among the many possible semi-synthetic strategies employed to increase the variety of chemical structures that can be applied in the search for novel bioactive compounds. In this paper we obtained ent-pimaradienoic acid (1, PA, ent-pimara-8(14),15-dien-19-oic acid) derivatives by fungal biotransformation using Aspergillus niger strains. To assess the ability of such compounds to inhibit vascular smooth muscle contraction, we also investigated their spasmolytic effect, along with another five PA derivatives previously obtained in our laboratory, on aortic rings isolated from male Wistar rats. The microbial transformation experiments were conducted at 30°C using submerged shaken liquid culture (120 rpm) for 10 days. One known compound, 7α-hydroxy ent-pimara-8(14),15-dien-19-oic acid (2), and three new derivatives, 1β-hydroxy ent-pimara-6,8(14),15-trien-19-oic acid (3), 1α,6β,14β-trihydroxy ent-pimara-7,15-dien-19-oic acid (4), and 1α,6β,7α,11α-tetrahydroxy ent-pimara-8(14),15-dien-19-oic acid (5), were isolated and identified on the basis of spectroscopic analyses and computational studies. The compounds obtained through biotransformation (2-5) did not display a significant antispasmodic activity (values ranging from 0% to 16.8% of inhibition); however the previously obtained diterpene, methyl 7α-hydroxy ent-pimara-8(14),15-dien-19-oate (8), showed to be very effective (82.5% of inhibition). In addition, our biological results highlight the importance to study the antispasmodic potential of a large number of novel diterpenes, to conduct further structure-activity relationship investigations.

Microbial Transformations of Plant Secondary Metabolites

“…1), ent-pimara-8(14),15-dien-19-oic acid, present in roots of Aralia cordata, was transformed by Aspergillus niger strains into four entpimaradienoic acid derivatives through reactions of hydroxylation, C6-C7 dehydrogenation, and transmigration of the double bond from C8-C14 to C7-C8. The methyl 17α-hydroxy-ent-pimara-8(14),15-dien-19-oate obtained was more effective than the substrate [68]. Diterpenes dehydroabietanol, obtained from Juniperus phoenicea and Salvia pomifera, and teideadiol ( Fig.…”

The use of Aspergillus niger cultures for biotransformation of terpenoids

“…Isostevic acid (CLXIII) is hydroxylated by A. niger BCRC 32720 to eight metabolites with anti-inflammatory properties [80]: Stemodin (CLXVII), a tetracyclic diterpenoid produced by the seaside twintip plant of Jamaica, is biotransformed in cultures of A. niger ATCC 9142 to 2␣,3␤,13-, 2␣,7␤,13-, and 2␣,13,16␤-trihydroxystemodane [67]. The same strain also transforms stemodinone (CLXVIII) to 13,18-and 13,16␤-dihydroxystemodan-2-one; and it transforms stemarin (CLXIX) to four metabolites, including three carboxylic acids [82]: ent-Pimaradienoic acid (CLXXXVII), an antibacterial diterpenoid from a Chinese yew tree, is derivatized by biotransformation with a strain of A. niger to 7␣-hydroxy-ent-pimara-8(14),15-dien-19-oic acid, 1␤-hydroxy-ent-pimara- 6,8(14),15-trien-19-oic acid, 1␣,6␤,14␤-trihydroxy-ent-pimara-7,15-dien-19-oic acid, and 1␣,6␤,7␣,11␣-tetrahydroxy-ent-pimara-8(14),15-dien-19-oic acid [91]: Triptonide (CLXXXVIII), a diterpenoid triepoxide lactone from a Chinese medicinal vine, has anti-inflammatory and antitumor activity but also significant toxicity. A. niger AS 3.739 transforms it to the less toxic metabolites 5␣-hydroxytriptonide, triptolide (with a 14␤-hydroxyl group), 17-hydroxytriptonide, and 16-hydroxytriptonide without hydrolyzing any of the three epoxide groups [92]: …”

Microorganisms in Chemistry of Terpenoids

“…Isosteviol lactone (CLXXXI) is biotransformed by A. niger BCRC 31130 to seven different hydroxylated diterpenoids, some of which inhibit the activator protein-1 transcription factor (Chou et al, 2009). Isostevic acid (CLXXXII) is hydroxylated by A. niger BCRC 32720 to eight metabolites with anti-inflammatory properties (Yang et al,2012): One of them, 2α-hydroxy-5α,10β,14β-triacetoxytaxa-4(20),11(12)diene, has the potential to prevent resistance to chemotherapeutic drugs in some tumor cells : Neoandrographolide (CXCIX), a diterpenoid from a Chinese traditional medicinal plant, is biotransformed by A. niger AS 3.739 to five products: 8 (17), 13-ent-labdadien-16,15-olid-19oic acid, 19-hydroxy-8(17),13-ent-labdadien-16,15-olide, 18hydroxy-8(17),13-ent-labdadien-16,15-olid-19-oic acid, 3αhydroxy-8(17),13-ent-labdadien-16,15-olid-19-oic acid, and 8β,19-dihydroxy-ent-labd-13-en-16,15-olide (Chen et al, 2007): (14), 15-trien-19-oic acid, 1α,6β,14β-trihydroxy-ent-pimara-7,15-dien-19-oic acid, and 1α,6β,7α,11α-tetrahydroxy-ent-pimara-8(14),15-dien-19-oic acid (Severiano et al, 2013):…”