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1. Bacterial Biofilm Inhibition and Antifungal Activity of Neotropical Plants

Author

Ta, Chieu Anh Kim

Subjects
Quorum sensing, Q'eqchi' Maya, Naphthoquinone, Biofilm, Neotropical plants, Bioassay-guided isolation, Saponin, Traditional medicine, Antifungal
Abstract

This thesis examined the antimicrobial activity of select neotropical plants from Costa Rica and traditional Q’eqchi Maya medicines from Belize. In particular the potential for interference with bacterial quorum sensing (QS) and biofilm formation as well as fungal growth were assessed. Of one hundred and twenty six extracts collected from Costa Rica, one third showed significant QS inhibition while 13 species displayed more biofilm inhibitory activities than the positive control allicin. The active species belonged to the Lepidobotryaceae, Melastomataceae, Meliaceae, Sapindaceae, and Simaroubaceae. Twelve Marcgraviaceae species were tested for the same biological activities; of these, three showed similar QS inhibition to that of the positive control Delisea pulchra (Greville) Montagne and five with at least 30% biofilm inhibition. Only one species inhibited fungal growth – Marcgravia nervosa Triana & Planch. Bioassay-guided isolation of this plant resulted in the identification of the active principle as a naphthoquinone, with a minimum inhibitory concentration (MIC) ranging from 85 to 100 μM against Saccharomyces cerevisiae. Similarly, sixty one Q’eqchi’ Maya medicinal plant species were evaluated for their antimicrobial activities. Of these, four species showed more QS inhibition than D. pulchra, seven with comparable biofilm inhibitory activities that of allicin, and two with similarly antifungal activity to berberine. Two spirostanol saponins were isolated from Cestrum schlechtendahlii G.Don, an active antifungal plant. The major saponin showed growth inhibition against Saccharomyces cerevisiae and Fusarium graminearum, with MICs of 16.5 μM and 132 μM, respectively. Further analyses of this compound using chemical genomics suggested that its antifungal mechanism of action is pleiotropic, affecting multiple targets. Taken together, these findings showed that neotropical plants and traditional Q’eqchi’ Maya medicines contain phytochemicals that interfere with bacterial biofilm formation and quorum sensing as well as fungal growth.

Published
2015
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2. Antifungal Saponins from the Maya Medicinal Plant Cestrum schlechtendahlii G. Don (Solanaceae).

Author

Ta, Chieu Anh Kim, Guerrero ‐ Analco, J. Antonio, Roberts, Elizabeth, Liu, Rui, Mogg, Christopher D., Saleem, Ammar, Otárola ‐ Rojas, Marco, Poveda, Luis, Sanchez ‐ Vindas, Pablo, Cal, Victor, Caal, Federico, Subramaniam, Rajagopal, Smith, Myron L., and Arnason, John T.

Abstract

Bioassay-guided fractionation of the crude extract (80% EtOH) of the leaves of Cestrum schlechtendahlii, a plant used by Q'eqchi' Maya healers for treatment of athlete's foot, resulted in the isolation and identification of two spirostanol saponins (1 and 2). Structure elucidation by MS, 1D-NMR, and 2D-NMR spectroscopic methods identified them to be the known saponin (25R)-1β,2α-dihydroxy-5α-spirostan-3-β-yl-O-α-L-rhamnopyranosyl-(1 → 2)-β-D-galactopyranoside (1) and new saponin (25R)-1β,2α-dihydroxy-5α-spirostan-3-β-yl-O-β-D-galactopyranoside (2). While 2 showed little or no antifungal activity at the highest concentration tested, 1 inhibited growth of Saccharomyces cerevisiae (minimum inhibitory concentration (MIC) of 15-25 μM), Candida albicans, Cryptococcus neoformans, and Fusarium graminearum (MIC of 132-198 μM). [ABSTRACT FROM AUTHOR]

Published
2016
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3. Antimicrobial activities of Marcgraviaceae species and isolation of a naphthoquinone from Marcgravia nervosa (Marcgraviaceae).

Author

Carballo-Arce, Ana Francis, Ta, Chieu Anh Kim, Rocha, Marco Eduardo do Nascimento, Liu, Rui, Harmsen, Irene, Mogg, Christopher D., Otárola-Rojas, Marco, Garcia, Mario, Sanchez-Vindas, Pablo, Poveda, Luis, Subramaniam, Rajagopal, Smith, Myron L., Kaplan, Maria Auxiliadora Coelho, Figueiredo, Maria Raquel, Durst, Tony, and Arnason, John T.

Subjects
*ERICALES, *PLANT extracts, *BACTERICIDAL action, *QUORUM sensing, *CHROMOBACTERIUM violaceum, *PSEUDOMONAS aeruginosa, *SACCHAROMYCES cerevisiae
Abstract

The Marcgraviaceae is a neotropical plant family of lianas and shrubs distributed throughout Central and South America, mainly in evergreen and semi-evergreen tropical forests. In this study, extracts of 12 Marcgraviaceae species were assessed for inhibition of bacterial quorum sensing (QS) in Chromobacterium violaceum, bacterial biofilm formation in Pseudomonas aeruginosa PA14, and fungal growth in Saccharomyces cerevisiae. Six species showed promising inhibitory activities in at least one of the three bioassays ( Marcgravia nervosa Triana & Planch. , Marcgravia polyantha Delp. , Marcgravia schippii Standl. , Marcgraviastrum subsessile (Benth.) Bedell , Schwartzia brasiliensis (Choisy) Bedell ex Gir-Cañas , and Schwartzia costaricensis (Gilg.) Bedell). Analyses of the crude extract of the leaves of Marcgravia nervosa using HPLC-APCI-MS showed the presence of five pentacyclic triterpenes: ursolic acid ( 2), betulinic acid ( 3), α-amyrin ( 4), β-amyrin ( 5), lupeol ( 6). Bioassay-guided fractionation of this plant resulted in the isolation and identification of 2-methoxy-1,4-naphthoquinone ( 1) as the active principle with a minimum inhibitory concentration (MIC) of 85-100 μmol·L−1 against Saccharomyces cerevisiae BY4741 (haploid) and BY4743 (diploid). [ABSTRACT FROM AUTHOR]

Published
2015
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