Luis A. Loyola

Flavonoids as stabilizers of fish oil: An alternative to synthetic antioxidants

The antioxidant activities against fish oil oxidation of six commercially available flavonoids and of five flavonoids purified from two Chilean native plants were compared to those ofdl-α-tocopherol and of two synthetic antioxidants, butylated hydroxytoluene and butylated hydroxyanisole. Among the commercial flavonoids, catechin, morin and quercetin showed a higher activity when fish oil oxidation (either spontaneous or Fe2+-induced) was assessed from the formation of peroxides or thiobarbituric acid-reactive substances. Among the native flavonoids, the 5,3′,4′-trihydroxy-7-methoxy flavanone (designated as Pt-2) showed the highest antioxidant activity. Mixtures of quercetin or of Pt-2 withdl-α-tocopherol produced better inhibitory effects when compared to that of each substance assayed by itself. Also, when Pt-2 and quercetin were assayed in combination (0.3 g/kg oil and 0.7 g/kg oil, respectively), a synergistic antioxidant effect was observed. Results indicate that several flavonoids could be used as natural antioxidants as a means to replace those synthetic antioxidants, the use of which has been questioned.

Diterpenoids from Azorella yareta and their trichomonicidal activities

Diterpenoids with trichomonicidal activity were isolated from the aerial parts of Azorella yareta Hauman. One was 13beta-hydroxyazorellane, together with the known constituents mulinolic acid, mulin-11,13-dien-20-oic acid, azorellanol and 13alpha-hydroxyazorellane. Their structures were determined by spectroscopic and chemical methods.

Antimicrobial activity of three baccharis species used in the traditional medicine of Northern Chile.

The antimicrobial activities of aqueous ethanol and chloroform extracts of three Baccharis species currently used in Northern Chile folk medicine for the treatment of several infectious and inflammatory disorders were tested against Gram-positive and negative bacteria and fungal spp. using the agar-disc diffusion assay. The results indicated that the activity was more pronounced against Gram-positive than against Gram-negative bacteria and yeast. No significant differences on the antibacterial activity were observed in the aqueous ethanol versus chloroform extracts. None of the plant extracts evaluated exhibited any activity against ten fungi tested.

Antituberculosis activity of natural and semisynthetic azorellane and mulinane diterpenoids.

The antituberculosis activity of 14 natural azorellane and mulinane diterpenoids isolated from Azorella compacta, Azorella madreporica, Mulinum crassifolium, and Laretia acaulis, together with eight semisynthetic derivatives, was evaluated against two Mycobacterium tuberculosis strains. The natural azorellanes azorellanol (3) and 17-acetoxy-13-alpha-hydroxyazorellane (6), and the semisynthetic mulinanes 13-hydroxy-mulin-11-en-20-oic-acid methyl ester (13) and mulinenic acid methyl ester (23), showed the strongest activity, with MIC values of 12.5 microg/mL against both strains. The methylated derivatives 13-hydroxy-mulin-11-en-20-oic-acid methyl ester (13), mulin-11,13-dien-20-oic acid methyl ester (15) and mulinenic acid methyl ester (23) proved to be more active than the parent compounds.

Diterpenoids from Azorella compacta

In addition to mulinolic acid, a new diterpenoid, mulin-11,13-dien-20-oic acid, has been isolated from the aerial parts of Azorella compacta. Its structure was based on a spectroscopic comparison with mulinolic acid and on chemical grounds.

Mulinic and isomulinic acids. rearranged diterpenes with a new carbon skeleton from Mulinum crassifolium

Abstract Two new diterpenoids, mulinic and isomulinic acids, have been isolated from the aerial parts of Mulinum crassifolium (Umbelliferae). The structure of mulinic actd (1) was determined by a combination of spectroscopic and single-crystal X-ray diffraction analyses.The proposed structure of isomulinic acid (2) was based on spectroscopic comparison with mulinic acid and on chemical grounds. The diterpenoids 1 and 2 possess a novel carbon skeleton whose plausible biogenetic pathway from a suitable labdane derivative is briefly discussed.

Azorellanol: A diterpenoid with a new carbon skeleton from Azorella compacta

Abstract A new diterpenoid, azorellanol (5), was isolated from the whole plant of Azorella compacta (Umbelliferae). The structure was established by using mainly one- and two-dimensional NMR techniques, whereas the absolute stereochemistry was determined by X-ray diffraction analysis. The diterpenoid (5) possesses a novel hydrocarbon skeleton for which we suggest the name azorellane A new diterpenoid, azorellanol, was isolated from whole plant of Azorella compacta (Umbelliferae). The structure was established by using mainly one-and two-dimensional NMR technique, whereas the absolute stereochemistry was determined by X-ray diffraction analysis. The diterpenoid possesses a novel hydrocarbon skeleton for which we suggested the name azorellane. Download : Download full-size image

Mulinol, A diterpenoid from Azorella compacta

Abstract In addition to mulinic acid, a new diterpenoid, mulinol has been isolated from the aerial parts of Azorella compacta . Its structure was based on spectroscopic comparison with mulinolic acid and chemical grounds.

Mulinolic acid, a diterpenoid from Mulinum crassifolium

Abstract Mulinolic acid, a new diterpenoid, has been isolated from the aerial parts of Mulinum crassifolium . Its structure was established by spectroscopic means. Mulinolic acid has a rearranged mulinane carbon skeleton of the type which has been found in four other diterpenoids from the same plant.

17-Acetoxymulinic acid, a rearranged diterpenoid from Mulinum crassifolium

Abstract From the aerial parts of Mulinum crassifolium a new diterpenoid, 17-acetoxymulinic acid, has been isolated. Its structure was established by spectroscopic means and by comparison with a closely related compound (mulinic acid).