Calophyllum inophyllum is a large, nondeciduous tree native to a wide swath of regions including Central and East Africa; a north-to-south swath of India; Southeast Asia; Polynesia; the Philippines; and Australia. A member of the mangosteen family (Clusiaceae, also known as Guttiferae), C. inophyllum is now cultivated in much of the tropical world.
The oil derived from this abundant plant is known by a wide variety of names, including Alexandrian laurel, beach mahogany, beauty leaf, beach calophyllum, dilo, and kamani. But perhaps it is best known by the French Polynesian name: tamanu. Tamanu oil has been used for hundreds of years in cuisine and to treat various medical conditions. Ocular burn and cutaneous wound healing are some distinct conditions for which the oil of C. inophyllum has a long history of use in traditional folk medicine (Oncol. Rep. 2012;28:1096-102; Int. J. Cosmet. Sci. 2002;24:341-8).
Wound healing and eye protection
The C. inophyllum components to which wound-healing activity have been attributed include calophyllolide and inophyllum, as well as various polyphenols, many of which exert antioxidant effects (Int. J. Cosmet. Sci. 2002;24:341-8).
Modern research buttresses the use of tamanu oil for corneal protection from burns. In 2007, Said et al. explored the anti-UV activity of tamanu oil for eye protection. They found that the botanical oil displayed a significant capacity to absorb UV radiation, even at low concentrations (1/10,000, v/v), with a sun protection factor ranging from 18 to 22. Concentrations of C. inophyllum oil of up to 1% were not cytotoxic to human conjunctival epithelial cells, with the agent acting against oxidative stress and DNA damage. In light of the apparent antioxidant and cytoprotective effects of C. inophyllum oil in the study, the researchers concluded that the oil has potential as a natural UV filter in ophthalmic formulations (Eur. J. Pharm. Sci. 2007;30:203-10).
In 2009, Said et al. performed in vitro, in vivo, and ex vivo studies to assess the effects of different rinsing and healing protocols for alkali-induced ocular burn and inflammation in rabbits. The researchers used NaOH to induce corneal reactions in the rabbits, followed by rinses with NaCl 0.9% or controlled-ionization marine formula combined with N-acetylcysteine or vegetable oils (from C. inophyllum and Aleurites moluccana). The investigators assessed corneal epithelium regeneration and inflammatory cell infiltration using in vivo confocal microscopy and ex vivo histological cuts. They found that the combination of controlled-ionization marine solution with 10% C. inophyllum oil and 90% A. moluccana oil promoted corneal epithelium regeneration while reducing inflammatory cells, suggesting its viability as ocular burn therapy (Ophthalmologica 2009;223:52-9).
Other medical benefits
A wide range of health benefits have been ascribed to tamanu oil, and the ingredient has been found in an increasing number of topical products. It is thought to impart anti-inflammatory, antioxidant, antibacterial, antiviral, and photoprotective activity.
In 2011, Ayyanar et al. concluded a 4-year study intended to ascertain the herbs used in traditional medicine practiced by the Kani tribes in the Tirunelveli hills of Western Ghats, India. The researchers identified 90 species of plants used traditionally as ethnomedicinal treatments, with 65 different indications reported, particularly dermatologic conditions and gastrointestinal illnesses. Based on their study, they identified 16 species, including C. inophyllum, for additional ethnopharmacological investigation as potential sources of new drug agents (J. Ethnopharmacol. 2011;134:851-64).
In 2004, Yimdjo et al. investigated the chemical constituents of the root bark and nut of C. inophyllum, resulting in the isolation of several compounds and the discovery of antibacterial activity against several microbes (Phytochemistry 2004;65:2789-95).
C. inophyllum leaf extracts from the islands of French Polynesia have also been touted for several constituents that hold promise as anti-HIV-1 agents, including inophyllum B and P (Anal. Chim. Acta 2008;624:147-53). In addition, quantitative high-performance liquid chromatography (HPLC) analysis of callus cultures of C. inophyllum has revealed the anti-HIV activity of the dipyranocoumarins inophyllum B and P (J. Biotechnol. 2007;130:346-53).
Tamanu oil also has demonstrated potential use for humans and domestic animals as an insect repellent, specifically against the stable fly, Stomoxys calcitrans (J. Med. Entomol. 2010;47:575-80; Pest Manag. Sci. 2010;66:1191-8).
In 2012, Tsai et al. investigated the anti-inflammatory properties of an acetone extract of C. inophyllum leaves using lipopolysaccharide (LPS)-induced RAW 264.7 cells to assess the impact of the extract on nitric oxide (NO) expression and inducible nitric oxide synthase (iNOS). They found that C. inophyllum significantly inhibited, in dose-dependent fashion, the LPS-induced synthesis of NO, in addition to the expression of iNOS, cyclooxygenase (COX)-2, and nuclear factor–kappa B (NF-kappaB). The researchers concluded that the C. inophyllum extract exhibits anti-inflammatory activity and has potential application to inflammatory conditions in human beings (Oncol. Rep. 2012;28:1096-102).