The need to control microbial activity is inherent in two major facets of personal care. The first area is that of antimicrobial care where the product helps to retard the growth of topical pathogens or eliminates them. The second is in the area of preservatives that retard the growth of microbes in product formulations.

Recently there has been increased dialogue related to natural antimicrobials as topical actives and preservatives in the personal care industry. Synthetic compounds long accepted as effective in controlling microbial growth have come under scientific and regulatory scrutiny. These efforts are mainly driven by safety and environmental concerns, and the increased incidence of antibiotic resistant microbial strains. Natural alternatives derived from botanicals are therefore being explored by researchers around the world.

In a series of posts, I’m going to focus on some of the natural antimicrobials that are currently being investigated or have been put into use in major market cosmetics.

Coleus oil [INCI: Coleus forskohlii root oil]

Coleus Root (illustration)

Coleus oil is an essential oil extracted from the roots of Coleus forskohlii, a plant from the Natural Order Labiatae (Lamiaceae), a family of mints and lavenders. This species is a perennial herb with fleshy, fibrous roots. This grows wild in the warm sub-tropical temperate areas in South Asia. The roots are eaten as a condiment or pickle in India. In recent years Coleus forskohlii has gained pharmacological importance as the only known plant source of the biologically active compound, forskolin, a coleus oil which is a useful by-product of forskolin extraction. The newly discovered antimicrobial properties of the oil (of specific composition obtained using a proprietary extraction process)[1] render it useful in topical preparations.

Compounds such as 3-decanone (about 7%), bornyl acetate (about 15%), sesquiterpene hydrocarbons and sesquiterpene alcohols in major concentrations impart pleasing spicy notes to the essential oil. ß-sesquiphellandrene (about 13%) and g-eudesmol (12.5%) were identified in experimental studies on the oil.

In laboratory studies, coleus oil was found to inhibit the growth of skin pathogens more effectively than the better known tea tree oil; the pathogens included Propionbacterium acnes, Staphylococcus aureus and Staphylococcus epidermidis. Additionally, coleus oil was found to inhibit the yeast culture Candida albicans more effectively than tea tree oil. The extract is safe to use in cosmetic formulations, it does not irritate the skin and its pleasant woody aroma blends with cosmetics.

References:

1. Bruneton, Jean. (1995) Coleus forskohlii. in Pharmacognosy, Phytochemistry, Medicinal Plants, Lavoisier publishing Company, 521.

2. de Souza, N.J. (1991) Coleus forskohlii Briq.- The Indian plant source for forskolin. Recent Advances in Medicinal, Aromatic & Spice crops, (ed: S..P. Raychaudhuri.) Today and

3. Tomorrow’s printers and Publishers, New Delhi, India, Vol I: 83-91. Misra, L.N. et al. (1994) Variability of the chemical composition of the essential oil of Coleus forskohlii genotypes. J. Essential Oil Res. 6:243-247.

4. Research Report, Sabinsa Corporation, 2001

5. Denver, C.V. et al. (1994) Isolation of antirhinoviral sesquiterpenes from ginger (Zingiber officinale). J Nat Prod. 57(5):658-62 .

6. Buchbauer G et al. (1992) Effects of valerian root oil, borneol, isoborneol, bornyl acetate and isobornyl acetate on the motility of laboratory animals (mice) after inhalation. Pharmazie. 47(8):620-2

7. Nishijima, S., et al. (2000) The bacteriology of acne vulgaris and antimicrobial susceptibility of Propionibacterium acnes and Staphylococcus epidermidis. J. Dermatol.. 27:318-323

8. Nishijima, S et al.(1994) Sensitivity of Staphylococcus aureus and Streptococcus pyogenes isolated from skin infections in 1992 to antimicrobial agents, J. Dermatol 21: 233-238.

9. Sanchez-Perez, L. and Enrique Acosta-Gio (2001) A. Caries risk assessment from dental plaque and salivary Streptococcus mutans counts on two culture media. Arch. Oral Biol., 46: 49-55.