Leonardo Castellanos

Cembranoid diterpenes from the Caribbean sea whip Eunicea knighti.

Three new cembranoid diterpenes, knightol (1), knightol acetate (2), and knightal (3), along with the known asperdiol (4) and asperdiol acetate (5), were isolated as major compounds from the sea whip Eunicea knighti collected from the Colombian Caribbean. The structures and absolute configurations of 1-5 were determined on the basis of spectroscopic analyses and by a combination of chemical and NMR methods, multiple correlations observed in a ROESY experiment, and using the modified Mosher method. Additionally, five semisynthetic compounds, 6-10, obtained during the chemical transformations of the natural compounds are here reported for the first time. All compounds were tested for antimicrobial activity against marine bacteria associated with heavily fouled surfaces and were also screened for antiquorum sensing (QS) activity. Compounds 1, 3, and 8 showed significant antimicrobial activity against bacterial isolates, and 1, 3, 7, and 8 showed excellent anti-QS inhibition activity measured by means of bioluminescence inhibition with biosensor model systems.

Passiflora manicata (Juss.) aqueous leaf extract protects against reactive oxygen species and protein glycation in vitro and ex vivo models.

The leaf extracts of many species of genus Passiflora have been extensively investigated for their biological activities on several rat tissues, but mainly in the central nervous system and liver. They posses anxiolytic-like, sedative effects and antioxidant properties. Evidences suggest a key role of C-glycosylflavonoids in the biological activities of Passiflora extracts. Some species (such as P. manicata) of the genus are still poorly investigated for their chemical and biological activity. In this work, we aim to investigate both antioxidant and antiglycation properties of aqueous extract of P. manicata leaves (PMLE) in vitro and ex vivo models. Crude extract showed the C-glycosylflavonoid isovitexin as the major compound. Isoorientin and vitexin were also identified. In TRAP/TAR assay, PMLE showed a significant antioxidant activity. PMLE at concentrations of 10 and 100 μg mL⁻¹ significantly decreasing LDH leakage in rat liver slices. Antioxidant effect also was observed by decreased in oxidative damage markers in slices hence hydrogen peroxide was added as oxidative stress inductor. PMLE inhibited protein glycation at all concentrations tested. In summary, P. manicata aqueous leaf extract possess protective properties against reactive oxygen species and also protein glycation, and could be considered a new source of natural antioxidants.

Ophirasterol, a new C31 sterol from the marine sponge Topsentia ophiraphidites.

Analysis of the sterol fraction obtained from the Colombian Caribbean sponge Topsentia ophiraphidites revealed that this sponge is a rich source of C30 and C31 sterols. Among them, a new C31 sterol, named ophirasterol, was isolated, and its structure was established as (22E,24R)-24-(1-buten-2-yl)cholesta-5,22-dien-3beta-ol (1) by spectral means and comparison with synthetic C-24 epimers with known configuration. Other isolated C30 and C31 sterols were the known 24-ethyl-24-methyl-22-dehydrocholesterol (2), 24-isopropyl-22-dehydrocholesterol (3), 24-isopropylcholesterol (4), 24-ethyl-24-methylcholesterol (5), 24-isopropenyl-25-methyl-22-dehydrocholesterol (6) and 24-isopropenyl-25-methylcholesterol (7), and 24-isopropenyl-22-dehydrocholesterol (8).

Glycosylflavonoids from Cecropia pachystachya Trécul are quorum sensing inhibitors.

The Cecropia genus is widely distributed in Latin America including at least 60 species, and some of them are commonly used in traditional medicine for the treatment of several diseases. We used Cecropia pachystachya Trécul to search for quorum sensing (QS) inhibitors compounds and found that the aqueous extract of C. pachystachya leaves is a promising source of substances with this activity. Using as biosensor Chromobacterium violaceum ATCC 31532 and Escherichia coli pSB403, the compounds chlorogenic acid (2), isoorientin (3), orientin (4), isovitexin (6), vitexin (7), and rutin (9) were identified as QS inhibitors. None of these compounds inhibited the growth of neither the used biosensors nor the microorganisms Staphylococcus aureus ATCC 23591, Escherichia coli ATCC 25922 and Saccharomyces cerevisiae, used here as growth inhibition controls. Along with the rutin, here we presented for the first time the QS-inhibition potential of the C-glycosyl flavonoids. The prospective of this evidence lead to the use of these compounds as antipathogenic drugs or antifoulants.

Dolabelladienols A-C, new diterpenes isolated from Brazilian brown alga Dictyota pfaffii.

The marine brown alga Dictyota pfaffii from Atol das Rocas, in Northeast Brazil is a rich source of dolabellane diterpene, which has the potential to be used in future antiviral drugs by inhibiting reverse transcriptase (RT) of HIV-1. Reexamination of the minor diterpene constituents yielded three new dolabellane diterpenes, (1R*,2E,4R*,7S,10S*,11S*,12R*)10,18-diacetoxy-7-hydroxy-2,8(17)-dolabelladiene (1), (1R*,2E,4R*,7R*,10S*,11S*,12R*)10,18-diacetoxy-7-hydroxy-2,8(17)-dolabelladiene (2), (1R*,2E,4R*,8E,10S*,11S,12R*)10,18-diacetoxy-7-hydroxy-2,8-dolabelladiene (3), termed dolabelladienols A–C (1–3) respectively, in addition to the known dolabellane diterpenes (4–6). The elucidation of the compounds 1–3 was assigned by 1D and 2D NMR, MS, optical rotation and molecular modeling, along with the relative configuration of compound 4 and the absolute configuration of 5 by X-ray diffraction. The potent anti-HIV-1 activities displayed by compounds 1 and 2 (IC50 = 2.9 and 4.1 μM), which were more active than even the known dolabelladienetriol 4, and the low cytotoxic activity against MT-2 lymphocyte tumor cells indicated that these compounds are promising anti-HIV-1 agents.

Fuscoside E: A strong anti-inflammatory diterpene from Caribbean octocoral Eunicea fusca

The screen of 10 soft coral extracts collected from the Colombian Caribbean Sea in the TPA-induced ear edema model allowed us to identify Eunicea fusca extract among others as an interesting source of active compounds. The new diterpene, fuscoside E (1), along with the known fuscoside B (2), fuscol (3), (+)-germacrene D (4) and a mixture of six sterols (5-10), were isolated from this soft coral. Their structures were elucidated by 1D and 2D NMR spectroscopy techniques. Fuscoside E (1) absolute stereochemistry was determined by chiroptical methods. Fuscoside E (1) and B (2) showed strong anti-inflammatory in the above mentioned bioassay. Additionally, fuscoside E (1) and the sterol mixture (5-10) presented antifouling activity against bacterial strains involved in surface colonization.

Synthesis of cembranoid analogues and evaluation of their potential as quorum sensing inhibitors

Natural cembranoids have shown Quorum Sensing Inhibitory (QSI) activity, but their structure-function interactions are not well understood. Thirty-four cembranoid analogues were synthesized using six natural cembranoids (1-6) previously isolated from the Colombian Caribbean octocorals Eunicea knighti and Pseudoplexaura flagellosa as lead compounds. The analogues (7-40) obtained through the selected chemical transformations were tested in vitro against the QS systems of a Chromobacterium violaceum biosensor. Half of the cembranoid analogues assayed showed superior QSI activity to the lead compounds; three (8, 13, and 18) displayed remarkable potency up to three times higher than the natural compounds. Thereby, we have synthesized a pool of cembranoid QS inhibitors that can be used in concert with natural compounds to develop antipathogenic drugs and antifouling agents.

Phylogenetic analysis of the order Halichondrida (Porifera, Demospongiae), using 3β-hydroxysterols as chemical characters

To analyze and extract phylogenetic information from chemical characters, the 3b-hydroxysterol composition of 12 sponge species of various families of the Poriferan order Halichondrida (sensu lato), was determined. The current definition of the order is ambiguous, and its classification remains in a state of flux and hence, further chemical characters may aid in stabilizing it. Axinella corrugata, Pseudaxinella reticulata, P. explicata, Ptilocaulis walpersi, Dragmaxia undata (family Axinellidae), Myrmekioderma rea, M. gyroderma(family Desmoxyidae), Scopalina ruetzleri (family Dictyonellidae), Halichondria lutea, H. magniconulosa, Topsentia ophiraphidites and Petromica ciocalyptoides (family Halichondriidae) were collected in the Santa Marta area, Colombian Caribbean. Cladistic principles were used to advance a hypothesis of genealogical relationship among the studied species and to contrast current classifications at various taxonomic ranks. Sterol identity and various sterol properties (number of carbons, nuclei type, saturations and substitutions of the lateral chain) were coded as discrete characters according to their relative abundance in 4% ranges, for each of the studied species, and for an out group of 41 species of nine orders whose sterol fractions had been published. Of more than 300 codified characters, 74 constituted unique evolutionary novelties within the studied in group. Fifty-one of these characters (including 15 sterols) uniquely defined six species. Twelve sets of novel characters were shared exclusively by two or more species of the studied group and were thus informative in a phylogenetic sense. The cladogram, built by hand, had seven characters that were compatible with each other and were shared by two or more species (i.e. synapomorphies) and five that were incompatible with two or more. However

VITEXIN DERIVATIVES AS CHEMICAL MARKERS IN THE DIFFERENTIATION OF THE CLOSELY RELATED SPECIES PASSIFLORA ALATA CURTIS AND PASSIFLORA QUADRANGULARIS LINN

The species of Passiflora are widely used in folk medicine as mild sedatives and tranquilizers. P. alata and P. quadrangularis are distributed throughout South America, with widespread occurrence in Brazil and Colombia. Due to the difficulty in making a botanical distinction between these species, especially in the absence of flowers and fruits, the use of chemical markers for these plants offer an alternative method of identification. This work describes the isolation and identification of the major flavonoids and saponins from the leaves of P. alata and P. quadrangularis, as well as rapid and efficient HPLC-DAD methods for comparison of these compounds in both species. Vitexin derivatives are proposed as chemical markers in the identification of P. alata and P. quadrangularis and the detection of adulterations in raw material.

Isolation of C-glycosylflavonoids with α-glucosidase inhibitory activity from Passiflora bogotensis Benth by gradient high-speed counter-current chromatography

In this study, we applied a gradient High-Speed Counter-Current Chromatography (HSCCC) method that allowed, by direct injection of an aqueous crude extract of the leaves of Passiflora bogotensis, the successful isolation of six flavonoids in a single run, with purity of each compound higher than 81%. This separation enabled the isolation of two new flavonoid glycosides, apigenin-6-C-α-l-rhamnopyranosyl-(1→2)-(6″-O-acetyl)-β-d-glucopyranoside (2) and luteolin-6-C-α-l-rhamnopyranosyl-(1→2)-(6″-O-acetyl)-β-d-glucopyranoside (4), and four known ones, isovitexin (1), isoorientin (3), isovitexin-2″-O-rhamnoside (5) and isoorientin-2″-O-rhamnoside (6). The structures of the isolated compounds were identified by HPLC-DAD, LC-MS, (1)H and (13)C NMR and comparison with literature data. The inhibitory activities of all of these compounds were evaluated in vitro on α-glucosidase from S. cerevisiae, and the IC50 was determinate. This is the first study concerning the chemical composition and biological activity of Passiflora bogotensis.