Abstract: In this study, the in vitro bacterial growth inhibition, antioxidant activity and the content in bioactive components of Plectranthus barbatus, P. hadiensis var. tomentosus, P. madagascarensis, P. neochilus and P. verticillatus aqueous extracts were investigated and compared by three extraction methods (infusion, decoction and microwave extractions). The microwave extract of P. madagascariensis showed the higher antimicrobial activity against the Staphylococcus epidermidis strain with a minimum inhibitory concentration of 40 µg/mL. This extract also showed no toxicity in a general toxicity assay and no considerable cytotoxicity against a human keratinocyte cell line. The antioxidant activity of the extracts was assessed using 2,2-diphenyl-1-picrylhydrazyl (DPPH method), and all showed antioxidant activity. The microwave extract of P. madagascariensis was the one with the highest antioxidant activity (IC50 value of 41.66 µg/mL). To increase extract stability, the microwave P. madagascariensis extract was then successfully encapsulated into alginate beads with high efficiency. This effective and low-cost strategy seems to be easy to extrapolate to an industrial scale with a future application on the skin.
Keywords: Plectranthus; antimicrobial activity; antioxidant activity; polymeric beads; alginate; extraction methods
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Rijo, P.; Matias, D.; Fernandes, A.S.; Simões, M.F.; Nicolai, M.; Reis, C.P. Antimicrobial Plant Extracts Encapsulated into Polymeric Beads for Potential Application on the Skin. Polymers 2014, 6, 479-490.
Rijo P, Matias D, Fernandes AS, Simões MF, Nicolai M, Reis CP. Antimicrobial Plant Extracts Encapsulated into Polymeric Beads for Potential Application on the Skin. Polymers. 2014; 6(2):479-490.
Rijo, Patrícia; Matias, Diogo; Fernandes, Ana S.; Simões, M. F.; Nicolai, Marisa; Reis, Catarina P. 2014. "Antimicrobial Plant Extracts Encapsulated into Polymeric Beads for Potential Application on the Skin." Polymers 6, no. 2: 479-490.