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 (IC 50 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. OPEN ACCESSPolymers 2014, 6 480

DHR seems to be a promising starting material with anticancer properties to further be explored.

Cytotoxicity screenings have identified Plectranthus plants as potential sources of antitumor lead compounds. In this work, several extracts from Plectranthus madagascariensis were prepared using different solvents (acetone, methanol, and supercritical CO 2 ) and extraction techniques (maceration, ultrasound-assisted, and supercritical fluid extraction), and their chemical composition was detailed using high-performance liquid chromatography with a diode array detector. The cytotoxic activity of the major compounds identified, namely, rosmarinic acid ( 1 ) and abietane diterpenes 7α,6β-dihydroxyroyleanone ( 2 ), 7α-formyloxy-6β-hydroxyroyleanone ( 3 ), 7α-acetoxy-6β-hydroxyroyleanone ( 4 ), and coleon U ( 5 ), was evaluated in a battery of human cancer cell lines, including breast (MDA-MB-231, MCF-7), colon (HCT116), and lung (NCI-H460, NCI-H460/R) cancer, and also in healthy lung (MCR-5) cells. Royleanone ( 3 ) was isolated for the first time from P. madagascariensis , and its full spectroscopic characterization (proton and carbon nuclear magnetic resonance) was accomplished. A high selectivity for lung cancer cells was observed for royleanones ( 2 , 4 ) with selectivity indexes of 4.3 and 3.2, respectively. The observed results combined with literature data allowed the establishment of important structure–activity relationships for substituted royleanone abietanes, such as the requirement for an electron-donating group at positions 6 and/or 7 in the abietane skeleton, and an improved cytotoxic effect for substituents with log P values between 2 and 5.

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Plectranthus ecklonii Benth. has widespread ethnobotanical use in African folk medicine for its medicinal properties in skin conditions. In this study, two different basic formulations containing P. ecklonii extracts were prepared, one in an organic solvent and the other using water. The aqueous extract only contained rosmarinic acid (RA) at 2.02 mM, and the organic extract contained RA and parvifloron D at 0.29 and 3.13 mM, respectively. RA in aqueous solution permeated skin; however, in P. ecklonii organic extract, this was not detected. Thus, P. ecklonii aqueous extract was further studied and combined with benzophenone-4, which elevated the sun protection factor (SPF) by 19.49%. No significant cytotoxic effects were observed from the aqueous extract. The Staphylococcus epidermidis strain was used to determine a minimum inhibitory concentration (MIC) value of 10 µg·mL−1. The aqueous extract inhibited the activity of acetylcholinesterase by 59.14 ± 4.97%, and the IC50 value was 12.9 µg·mL−1. The association of the P. ecklonii extract with a UV filter substantially elevated its SPF efficacy. Following the multiple bioactivities of the extract and its active substances, a finished product could be claimed as a multifunctional cosmeceutical with broad skin valuable effects, from UV protection to antiaging action.