Juan A. Garbarino

Antimicrobial and antibiofilm activity of secondary metabolites of lichens against methicillin-resistant Staphylococcus aureus strains from cystic fibrosis patients

AIMnThree secondary metabolites of lichens - usnic acid, atranorin and fumarprotocetraric acid - were evaluated for their in vitro antibacterial and antibiofilm activities against three strains each of methicillin-susceptible and methicillin-resistant Staphylococcus aureus (MRSA) from cystic fibrosis patients.nnnMATERIALS & METHODSnAntibacterial activity was assessed by broth microdilution, while antibiofilm activity was evaluated by spectrophotometry or viable count.nnnRESULTSnUsnic acid was significantly more active than atranorin against planktonic cells, while fumarprotocetraric acid exhibited no activity. Atranorin was the most effective in counteracting adhesion to polystyrene, although usnic acid was more active against MRSA. Usnic acid and atranorin showed comparable activity against biofilm formation, although atranorin was more active against MRSA. Usnic acid was significantly more active than atranorin against preformed biofilms.nnnCONCLUSIONnSecondary metabolites of lichens may be considered to be lead compounds for the development of novel molecules for the treatment of S. aureus infections in cystic fibrosis patients.

Chemistry of the Calceolaria Genus. Structural and Biological Aspects

Autochthonous species of the Calceolaria (Scrophulariaceae) genus are studied. From their apolar extracts 55 new diterpenes of six skeleton types, naphtoquinones and flavonoids have been isolated. Among the different diterpenes malonic substitutions and bis-diterpenes in which both units are joined by a malonic acid unit stand out. Pimaranes present C-9 epimerisation and, consequently, H-9 has the same orientation as Me-20. From C.sessilis naphthoquinones with antichagasic activity have been isolated; and the biotransformation of 2α,19-dihydroxy-9-epi-entpimara-7,15-diene with Giberella fujikuroi produced 7 new diterpenes.

Biotransformation of two ent-Pimara-9(11),15-diene derivatives by Gibberella fujikuroi

The incubation of 19-hydroxy-13-epi-ent-pimara-9(11),15-diene (4) with Gibberella fujikuroi gave 8 alpha,19-dihydroxy-9 alpha,11alpha-epoxy-13-epi-ent-pimara-15-ene (6), 7-oxo-11 alpha,19-dihydroxy-13-epi-ent-pimara-8(9),15-diene (7), 7-oxo-11beta,19-dihydroxy-13-epi-ent-pimara-8(9),15-diene (9), and 8 alpha,19-dihydroxy-9 alpha,11 alpha:15,16-diepoxy-13-epi-ent-pimarane (11), while the feeding of 13-epi-ent-pimara-9(11),15-diene-19-oic acid (5) with this fungus afforded 1-oxo-2 alpha,9 alpha-dihydroxy-13-epi-ent-pimara-11,15-dien-19-oic acid (13), 1-oxo-2 beta,9 alpha-dihydroxy-13-epi-ent-pimara-11,15-dien-19-oic acid (14), 13-epi-ent-pimara-9(11),15-dien-1,19-dioic acid 1,2-lactone (15), and 1-oxo-12 beta-hydroxy-13-epi-ent-pimara-9(11),15-dien-19-oic acid (16). In both biotransformations, the main reaction was the epoxidation of the 9(11)-double bond, followed by rearrangement to afford allylic alcohols. The formation of lactone 15 represents the first time that a Baeyer-Villiger oxidation has been observed in a microbiological transformation with this fungus.

Diterpenoids from Calceolaria glandulifera1

Abstract Two new diterpenes and three known diterpenes have been isolated from the aerial parts of C. glandulifera. The structures of the new compounds were established by spectroscopic evidence as 19-malonyloxy-9-epi-ent-7,15-isopimaradiene and 19-hydroxy-9-epi-ent-7,15-isopimaradiene.

Sesquiterpenoids in Nolana coelestis

Abstract From the aerial parts of Nolana coelestis four new natural substances, 4-methyl-12-acetoxy-4,11(13)-cadinadiene, 4,12-diacetoxy-4,11(13)-cadinadien

The Incubation of 13a,17-Dihydroxystemodane with Cephalosporium aphidicola

The biotransformation of 13α,17-dihydroxystemodane (3) with the fungus Cephalosporium aphidicola afforded 13α,17,18-trihydroxystemodane (4), 3β,13α,17-tri-hydroxystemodane (5), 13α,17-dihydroxy-stemodan-18-oic acid (6), 3β,11β,13α,17-tetra-hydroxystemodane (7), 11β,13α,17,18-tetrahydroxystemodane (8) and 3β,13α,17,18-tetra-hydroxystemodane (9). The hydroxylation at C-18 of the substrate points to a biosynthetically-directed transformation, because aphidicolin (2) is hydroxylated at this carbon. However, the C-3(β) and C-11(β) hydroxylations seem to indicate a xenobiotic biotransformation.

Diterpenoids from Calceolaria glandulifera1Part 19 in the series “Diterpenoids from Calceolaria species.” For part 18, see Ref.[1].1

Abstract Two new diterpenes and three known diterpenes have been isolated from the aerial parts of C. glandulifera. The structures of the new compounds were established by spectroscopic evidence as 19-malonyloxy-9-epi-ent-7,15-isopimaradiene and 19-hydroxy-9-epi-ent-7,15-isopimaradiene.