Hydnocarpus wightianus

In India: It grows in tropical forests along western Ghats, along the coast from Maharashtra to Kerala, Assam, Tripura, often planted on road sides in hilly areas.

Other countries: The tree is found in South East Asia, chiefly in the Indo-Malayan region, and cultivated in Sri Lanka, Nigeria and Uganda.[6]

The oil is semi-solid at room temperature and does not have a strong odor. Gas–liquid chromatography analysis has shown the oil to contain the following fatty acids – hydnocarpic acid, chaulmoogric acid, gorlic acid, lower cyclic homologues, myristic acid, palmitic acid, stearic acid, palmitoleic acid, oleic acid, linoleic acid and linolenic acid.[8] The oil is unusual in not being made up of straight chain fatty acids but acids with a cyclic group at the end of the chain.[9]

The crude oil is of pale greenish-brown tinged. The oil can be easily into white, watery oil. The oil contains three cyclopentene fatty acids.

Table: fatty acid composition of oil[10]

Table of physical properties of oil[11]

Seeds are ovoid, irregular and angular, 1 to 1 1/4 inches long, 1 inch wide, skin smooth, grey, brittle; kernel oily and dark brown. A fatty oil is obtained by expression, known officially as Gynocardia oil in Britain, as Oleum Chaulmoograe in the U.S.[12]

Fruits are plucked by climbing the tree or using long sticks with a sickle tied to it. The fruits are peeled by knife and the seeds are washed in water and then dried in sun. Seeds are decorticated (dehusked) by mallet, hand hammer, or decoricator. They may also be crushed in an expeller and rotary. The kernels yield 43% oil. The extracted oil is stored in zinc barrels until exported.[6]

The Molokai island in Hawaii once the "Land of the Living Death," where lepers were treated with remarkable success by the then new chaulmoogra oil. Photo from 1922

Chaulmoogra oil was commonly used in the early 20th century for the treatment of leprosy, used as intravenous injections.

The active ingredient that produces antimicrobial activity has been identified as hydnocarpic acid, a lipophilic compound. It acts by being an antagonist of biotin.[13] The oil was used intravenously or intramuscularly in the early part of the 20th-century against leprosy. An ethyl ester of the oil was developed by Alice Ball in 1916[14] which led to the preparation and marketing of it by Burroughs Wellcome (modern GlaxoSmithKline) in the early 1920s. The oil preparations were used intravenously for leprosy patients, often producing local reactions. The oil was often obtained directly from trees in India, Sri Lanka or Africa. Doctors would locally prepare ethyl esters to treat their patients. In June 1927, Burroughs Wellcome released the commercial preparation, sodium hydnocarpate marketed as Alepol, which produced lesser disagreeable symptoms of pain, swelling, irritating cough and blocking of the veins. In May 1928, doctors reported cure of leprosy in some patients after treatment with alepol.[15] In the 1940s chaulmoogra oil was replaced by the more effective sulfones.[14]

The oil contains 5′-methoxyhydnocarpin, an amphipathic weak acid.[16] Although a minor component in the oil with no antimicrobial activity on its own, it plays a role in preventing multidrug resistance among some bacteria such as Staphylococcus aureus. It enhances the action of berberine (which is not found in chaulmoogra oil) by preventing its removal from within Staphylococcus aureus bacterial cells. Thus using the oil or an extract of the hydnocarpic acid in combination with extracts from other plants could help increase antimicrobial activity due to synergistic effects.[17]

In view of its anti-mycobacterial activity, in 1922 it was also experimentally tried on other conditions caused by mycobacteria such as tuberculous laryngitis.[18]