PSEUDOPTEROGORGIA ELISABETHAE FROM SAN ANDRÉS AND PROVIDENCIA, A FEATHER FROM THE SEA WITH EXCELLENT POTENTIAL AS A SOURCE OF NATURAL PRODUCTS WITH INDUSTRIAL APPLICATION

Abstract

Pseudopterogorgia elisabethae, an interesting sea feather found in the islands of San Andrés and Providencia (SW Colombian Caribbean), has been the subject of our research studies for the last 7 years. In the first step of the studies here presented we collected fragments of individual colonies at various sites and depth ranges around the islands. Collected samples were extracted with CH₂ Cl₂ /MeOH and then subjected to HPLC-MS. Chromatographic profiles of the extracts, allowed us to recognize two different chemotypes for P. elisabethae. Chemotype 1 characterized samples from Providencia whereas chemotype 2 characterized samples from San Andres. Chemotype 1 was characteristic and exclusive of samples collected at Providencia. Chemotype 2 was characteristic but not exclusive to samples collected at San Andres, occasionally was found in samples from Providencia.

Each extract from the both chemotypes was fractionated by chromatographic means and the pure isolated compounds thus obtained were carefully identified by spectroscopic and chemical methods. A complex mixture (4-16%) of 13 compounds (pseudopterosins, seco-pseudopterosins and amphilectosins) characterized chemotype 1. Those were identified as follows: eight new compounds in nature, PsP, Q, R, and S glycosylated at C-10 with free and acetylated at C-4’, C- 3’ and C-2’ L-fucose, respectively, PsT, U and V glycosylated with D-arabinose free and acetylated at C-4’ and C-3’, respectively and the seco-PsK, glycosylated at C-7 with free L-fucose and five known compounds, PsG, K, seco-PsJ and amphilectosins A and B.

Chemotype 2 contained lesser amounts (2-4%) of the compounds mentioned above. In contrast it showed as major constituents an interconverting 1:1 mixture of non glycosylated amphilectane type diterpenes (IMNGD) (10-acetoxi-9-hydroxy-amphilecta-8,10,12,14 tetraene and 9-acetoxy- 10-hydroxy-amphilecta-8,10,12,14 tetraene) and minor amounts of elisabethatrienol and amphilecta- 8(13),11,14-triene-9,10-dione.

Subsequently, the evaluation of the anti-inflamatory properties in vivo of extracts (chemotype 1 and chemotype 2) was carried out by using the TPA-induced ear oedema model, classical experiment of acute inflammation and by inhibiting the MPA mediator released to the oedema tissues. The results showed relatively low levels of inflammation inhibition, when compared to the activity showed by the anti-inflammatory commercial drug indomethacin. In contrast, we found marked inhibition of MPO levels by both extracts, even superior to the inhibition shown by indomethacin. Additionally, in the in vitro MPO assay IMNGD, PsQ, PsS, PsT and PsU exhibited higher levels of inhibition compared with indomethacin and dexamethasone. In the NO release in vitro, IMNGD, PsP and PsT were the most potent treatments. On the other hand, PsQ, PsS and PsU did show NO scavenger activity but PsG, PsP and seco-PsK did not exhibit any scavenger activity. The latter compounds should inhibit the inducible Nitric Oxide Synthase (iNOS) or other routes that influence this enzyme.

The cytotoxicity activity of the compounds isolated from P. elisabethae was studied by the MTT assay, using the following cell lines: HEp-2 (carcinoma of the larynx), MKN-45 (stomach cancer), HT-29 (adenocarcinoma of the colon), MCF-7 (breast cancer) y HeLa (cervix cancer) and two fibroblast culture of normal cells. The results showed that both the chemotype 1 as the chemotype 2 presented promising activity against all cancer cell lines used. However, the extract of chemotype 1 was more potent that of the chemotype 2.

In the antimicrobial assays all pseudopterosins, seco-pseudopterosins and the IMNGD isolated from P. elisabethae exhibited selective activity against marine and pathogenic terrestrial gram positive bacteria (IC₅₀ values between 1.4-17 μg/ml) but they did not show any activity against Candida albicans.

Finally, in regard to the marine antifouling laboratory bioassays used to evaluate the antifouling properties of the compounds isolated during this work from the chemotype 1 of P. elisabethae, against marine organisms representative of micro- and macrofouling, the results showed that the crude extract, fractions containing pseudopterosins, seco-pseudopterosins and amphilectosins, and PsQ and PsU had promising antifouling power in concentrations about 1 μg/ml. The research in this direction still continues in our laboratory.

In conclusion, all results presented here contribute to demonstrate that the compounds isolated from the sea P. elisabethae are promising molecules having an interesting anti-inflamatory, cytotoxyc, antibacterial and antifouling activity profile. This fact makes this marine organism an attractive source of compounds which could be used in the industry.