Physic nut (purging nut, Barbados nut) is cultivated in Central and South America, Southeast Asia and Africa. These trees are planted as a living fence around the fields for their protection. The seeds are toxic to warms, insects, snails, rodents, humans and farm livestock. Essential oil, extracted from the seeds of purging nut and also termed as Jatropha oil against termites (esp. subterranean), contain insect-repelling active ingredient – phorobol esters.
“Phorbol esters are the tetracyclic diterpenoids generally known for their tumor promoting activity. They mimic the action of diacyl glycerol (DAG), activator of protein kinase C, which regulates different signal transduction pathways and other cellular metabolic activities. Besides, possessing antinutritional and toxic effects, few derivatives of the phorbol esters are also known for their antimicrobial and antitumor activities. The molluscicidal and insecticidal properties of phorbol esters indicate its potential to be used as an effective biopesticide and insecticide.” 1
Due to phorobol esters effect, physic oil is traditionally used as an insect repellent, rodenticide and molluscicide.
Lab study of physic (purging, barbados) nut oil in a sand barrier against subterranean termites
Jatropha oil against termites was tested in the laboratory of Deptartment of Forest Products and Paper Science, College of Forestry and Natural Resources, University of the Philippines Los Banos. It was evaluated for its barrier (antifeeding, antitunneling) and repellent action against the Philippine milk termite, Coptotermes vastator Light (Isoptera: Rhinotermitidae). Coptotermes vastator termite species are the main structural destructors of wood, which are foraging underground in the Philippines, Asia and Malaysia.
The study proved that the oil of physic nut showed anti-feeding effect, caused reduction of tunneling activity and enhanced the mortality of the subterranean termites. The wood insects were delivered and tested in a sand barrier treated with Jatropha curcas oil. Their behavior denoted that the oil is toxic and acts as a repellent.
Toxicity and repellent properties were higher than those reported for other naturally occurring compounds tested against the Formosan subterranean termite. 2
Concentration of Jatropha oil against termites, required for repelling and anti-feeding physical barriers
In fact, Jatropha oil against termites of 10% concentration proved to be a toxic, antifeeding or repelling barrier for Philippine subterranean species. Lower doses only reduced the tunneling activity, decreased cellulose-product consumption and caused a negligible increase in the termites’ mortality. Concentration level is likely to be problematic as potential application requires a large volume of oil to control feeding and tunneling activity of the subterranean Coptotermes vastator termite colony in sand barriers. In alternative, the oil of Barbados nut seeds can be applied for wood-coating treatment as a preservative measure to prevent termite attack.
In spite of the low toxicity to termites, Jatropha curcas oil remains an effective anti-termite agent due to the large sustainable supply of the material from Asia and Africa. The significant increase in termites’ activity can be achieved by enhancing its toxic components through extraction using organic solvents. Enhancing the amount of phorbol esters or curcin extracted using methanol (or acetone) indicated significant improvement in insecticidal and molluscicidal properties compared to crude Jatropha curcas extracts 3
- Goel G, Makkar H.P, Francis G., Becker K. Phorbol esters: structure, biological activity, and toxicity in animals (2007) ↩
- Cornelius ML, Grace JK, Yates JR. Toxicity of monoterpenoids and other natural products to the Formosan subterranean termite (Isoptera: Rhinotermitidae). Journal of Economic Entomology.1997;90:320–325 ↩
- Acda M.N.Toxicity, Tunneling and Feeding Behavior of the Termite, Coptotermes vastator, in Sand Treated with Oil of the Physic Nut, Jatropha curcas (2008) ↩