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Achillea millefolium (yarrow) is a traditionally used plant to treat wounds. The present study was conducted to evaluate the anti-acne activity of Achillea 'Moonshine', a hybrid variety of Achillea. The plant was extracted in four solvents-petroleum ether, ethyl acetate, ethanol and water. These extracts were screened for anti-microbial, free radical scavenging, anti-tyrosinase, anti-inflammatory activity and cytotoxicity assays necessary to characterize its anti-acne activity. The most promising activity was determined in the petroleum ether extract. The minimum inhibitory concentration (MIC) value for the petroleum ether extract was 0.83 mg/ml against Propioni bacterium acnes and 0.37 mg/ml against Staphylococcus. The minimum bactericidal concentration (MBC) value for petroleum ether was 0.83 and 0.75 mg/ml for P. acnes and Staphylococcus epidermidis, respectively. Though the ethyl acetate had a high flavonoid and phenolic content it was observed that the IC 50 values for the petroleum ether extract for free radical scavenging activity was 64.81 µg/ml, which was higher than ethyl acetate. Petroleum ether also showed tyrosinase inhibition at 0.033 mg/ml. The extract was also able to decrease the inflammatory cytokines like TNF-α and IL-8, and showed no cytotoxicity against dermal fibroblasts. These results suggest presence of active anti-acne phytochemicals in the petroleum ether extract, making it a novel plant candidate for the treatment of acne.

Achillea millefolium is a flowering plant in the family, Asteraceae and is known to be used in traditional medicine as astringent, stimulant, tonic, antiphlogistic and for the treatment of cold and influenza. In an earlier study in the authors' laboratory, four different extracts of a variety of yarrow called Achillea 'Moonshine' were tested for anti-acne effect. The petroleum ether extract of Achillea 'Moonshine' was demonstrated earlier in the authors' laboratory to have phytochemicals that could scavenge free radicals, inhibit growth of Propionibacterium acnes and reduce tyrosinase activity which are needed for acne treatment. Using column chromatography, the petroleum ether extract was fractionated and each fraction was tested against P. acnes using TLC bioautography. The active compound from TLC bioautography was isolated by HPLC and identified using Nuclear Magnetic Resonance and Mass Spectrometry studies. This led to characterization of a novel piperidide, N-(21-hydroxy-21-(piperidin-1-yl) henicosa-17, 19-diyl-1-yl) acetamide, from the petroleum ether extract of Achillea 'Moonshine' that contributed to the anti-acne activity. This study led to identification of a novel natural anti-acne compound that is anti-oxidant, anti-inflammatory and anti-microbial against acne causing organism.

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