Monoterpene Hydroxy Lactones Isolated from <i>Thalassiosira</i> sp. Microalga and Their Antibacterial and Antioxidant Activities
Alcina M. M. B. Morais,
Decha Kumla,
Valter F. R. Martins,
Ana Alves,
Luis Gales,
Artur M. S. Silva,
Paulo M. Costa,
Sharad Mistry,
Anake Kijjoa,
Rui M. S. C. Morais
Affiliations
Alcina M. M. B. Morais
CBQF—Centro de Biotecnologia e Química Fina—Laboratório Associado, Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua Diogo Botelho 1327, 4169-005 Porto, Portugal
Decha Kumla
CBQF—Centro de Biotecnologia e Química Fina—Laboratório Associado, Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua Diogo Botelho 1327, 4169-005 Porto, Portugal
Valter F. R. Martins
CBQF—Centro de Biotecnologia e Química Fina—Laboratório Associado, Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua Diogo Botelho 1327, 4169-005 Porto, Portugal
Ana Alves
CBQF—Centro de Biotecnologia e Química Fina—Laboratório Associado, Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua Diogo Botelho 1327, 4169-005 Porto, Portugal
Luis Gales
ICBAS—Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313 Porto, Portugal
Artur M. S. Silva
Departamento de Química & QOPNA, Universidade de Aveiro, 3810-193 Aveiro, Portugal
Paulo M. Costa
ICBAS—Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313 Porto, Portugal
Sharad Mistry
Department of Chemistry, University of Leicester, University Road, Leicester LE 7 RH, UK
Anake Kijjoa
ICBAS—Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313 Porto, Portugal
Rui M. S. C. Morais
CBQF—Centro de Biotecnologia e Química Fina—Laboratório Associado, Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua Diogo Botelho 1327, 4169-005 Porto, Portugal
Two monoterpenoid lactones, loliolide (1) and epi-loliolide (2), were isolated from the crude dichloromethane extract of a microalga, Thalassiosira sp.). The structures of loliolide (1) and epi-loliolide (2) were elucidated by 1D and 2D NMR analysis, as well as a comparison of their 1H or/and 13C NMR data with those reported in the literature. In the case of loliolide (1), the absolute configurations of its stereogenic carbons were confirmed by X-ray analysis, whereas those of epi-loliolide (2) were determined by NOESY correlations. Loliolide (1) and epi-loliolide (2) were tested for their growth inhibitory activity against two Gram-positive (Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212) and two Gram-negative (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853) bacteria, as well as one clinical isolate (E. coli SA/2, an extended-spectrum β-lactamase producer-ESBL) and two environmental isolates, S. aureus 74/24, a methicillin-resistant (MRSA), and E. faecalis B3/101, a vancomycin-resistant (VRE) isolates. The results showed that none of the tested compounds exhibited antibacterial activity at the highest concentrations tested (325 μM), and both revealed low antioxidant activity, with ORAC values of 2.786 ± 0.070 and 2.520 ± 0.319 µmol TE/100 mg for loliolide (1) and epi-loliolide (2), respectively.
