Pogostemon cablin, known in the West as patchouli or guang huo-xiang in China, is a long-time staple in traditional Chinese medicine for various indications, particularly gastrointestinal and skin disorders1.
Patchouli oil, which contains several mono- and sesquiterpenoids, alkaloids, and flavonoids, is thought to possess significant anti-inflammatory and antioxidant qualities2.In fact, it is reputed to impart antiviral, antioxidant, anti-inflammatory, and analgesic effects, and is also known to protect intestinal barrier function3. Peng et al. have found that patchouli oil exerts significant antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA)4.
After a comprehensive 2013 review, Chen et al. deemed P. cablin to have potential clinical benefits as an effective adaptogenic herbal treatment3. It is thought to have some antiacne properties as well1. Further, P. cablin is among the Top 10 most-often-used traditional Chinese medicine prescriptions for skin care and appearance1.
In Brazil, China, Indonesia, and Malaysia, P. cablin is cultivated for its essential oil, which plays an important role in the perfume industry. Patchouli essential oil, featured in perfumes, soaps, cosmetics, and as incense, is used by aromatherapists for its calming and reviving effects. The essential oil has also been shown to impart antioxidant activity5.
In 2014, Lin et al. studied the protective effects of P. cablin essential oil against ultraviolet (UV)-induced skin photoaging in mice. The researchers applied patchouli oil for 2 hours before UV exposure to the dorsal depilated skin of mice. They found that patchouli oil doses of 6 mg/mouse and 9 mg/mouse significantly suppressed skin wrinkle formation, mitigated skin elasticity impairment, and augmented collagen content (21.9% and 26.3%, respectively). The same doses also yielded significant reductions in epidermal thickness and malondialdehyde content, and blocked the disruption of collagen and elastic fibers. Patchouli oil treatment also resulted in the up-regulation of the antioxidant enzymes superoxide dismutase, glutathione peroxidase, and catalase. The investigators concluded that patchouli oil, perhaps due to its antioxidant characteristics, and sesquiterpene constituents in particular, was effective in preventing photoaging in mice, and warrants attention as a potential agent to hinder photoaging in humans1.
Feng et al. also investigated the effects of topically applied patchouli alcohol on UV-induced photoaging in mice that year. For 9 weeks, investigators applied patchouli oil solution or a vehicle to the depilated dorsal skin of 6-week-old mice. They found that patchouli oil significantly hastened the recovery of UV-induced skin lesions, which they ascribed to the antioxidant and anti-inflammatory activity of the agent and its down-regulation of the expression of matrix metalloproteinase (MMP)-1 and MMP-32.
Antimicrobial and mosquito repellent activity
In a 2005 study by Trongtokit et al. of the mosquito-repellent activity of 38 essential oils at three concentrations (10%, 50%, or undiluted) against the mosquito Aedes aegypti under laboratory conditions using human volunteers, undiluted P. cablin oil was one of four [along with Cymbopogon nardus (citronella), Syzygium aromaticum (clove), and Zanthoxylum limonella (Thai name: makaen)] undiluted oils to yield an effect, 2 hours of full repellency. The investigators then tested the same concentrations of these oils for repellency against Culex quinquefasciatus (the Southern house mosquito) and Anopheles dirus (the mosquito considered to be a vector of malaria in Asian forested zones. The undiluted oils provided the greatest protection, with clove oil rendering the most durable repellency6.
Wu et al. determined the acaricidal activity of compounds extracted from patchouli oil against the house dust mite (Dermatophagoides farinae) in 2012. They isolated 2-(1,3-dihydroxy-but-2-enylidene)-6-methyl-3-oxo-heptanoic acid (DHEMH), the hydrolysate of pogostone, and 15 other constituents in patchouli oil, ultimately ascertaining that DHEMH and patchouli oil itself were the most toxic substances to D. farinae. The investigators concluded that patchouli oil and DHEMH warrant consideration and more study for their acaricidal potential as environmentally friendly, effective, and simple fumigant alternatives to chemical agents7.
In 2013, Yang et al. used molecular docking technology to evaluate the antibacterial activity of patchouli oil in vitro. They identified 26 compounds in patchouli oil displaying antibacterial activity, with pogostone and (-)-patchouli alcohol exhibiting the strongest activity8. Later that year, Yang et al. used the same technology to establish that Herba pogostemonis oil exhibited potent antibacterial effects, especially the constituents pogostone and (-)-Herba pogostemonis alcohol9. Raharjo and Fatchiyah also used molecular docking tools and Chimera 1.7s viewer software in a virtual screening of compounds from patchouli oil, concluding that alpha-patchouli alcohol is a potential inhibitor of the cyclo-oxygenase (COX)-1 enzyme. This is notable given the pivotal role of COX-1 in the inflammatory response10.