Selective Solvent Extraction of the Bark of Rhizophora apiculata as an Anti-Termite Agent against Coptotermes gestroi

Abstract

The anti-termite action of the bark of mangrove plant Rhizophora apiculata and four other species against the attack of the subterranean termite Coptotermes gestroi was investigated. The bark powder was extracted and partitioned into four main extracts—petroleum ether (PE), chloroform (CE), ethyl acetate (EE), and n-butanol (BE). Termite bioassay on different extracts was carried out. The total phenol content (TPC) of the extracts was determined by the Folin-Ciocalteu method and expressed as gallic acid equivalent (GAE). Butylated hydroxytoluene (BHT) and Butylated hydroxyanisole (BHA) were used as a positive control in the free-radical-scavenging activity test. It was believed that both the toxicity and antioxidant properties of extractives imparted natural resistance to the bark of R. apiculata. Considering wood weight loss, EE appeared to be the most potent inhibitor. The EE was then fractionated into three fractions (F1, F2, F3) by means of thin layer chromatography. F2 exhibited the lowest mean percentage weight loss. Through chemical and spectral analyses, we attribute the presence of bioactive constituents in the EE to a mixture of aromatic carboxylic acids or phenolics.

Keywords:

• Anti-termite
• bark extracts
• Coptotermes gestroi
• phenolics
• Rhizophora apiculata

The researchers thank the Ministry of Science, Technology and Innovation (MOSTI) and the Universiti Sains Malaysia, Penang for providing the research grant EScience Fund (RM-9) 03-01-05-SF0334 or 305/PTEKIND/613323 that has made this work possible.

Notes

^a Values are means ± standard deviations from six replications. S, mahogany; R, mangrove; H, rubber; A, acacia and P, pine.

^a Values are means ± standard deviations from six replications. PE, petroleum ether; CE, chloroform; EE, ethyl acetate; BE, n-butanol extracts impregnated wood blocks (500 ppm each) and U1, untreated; P, petroleum ether; C, chloroform; E1, ethyl acetate; B, n-butanol solvents treated wood blocks served as control and added controls, respectively.

^a Values are means ± standard deviations from six replications. F1, fraction 1; F2, fraction 2; F3, fraction 3 impregnated wood blocks (500 ppm each) and U2, untreated; E2, ethyl acetate solvent treated wood blocks served as control and added control, respectively.

∗Values are means ± standard deviations from three replications; GAE, gallic acid equivalent.

∗Values are means ± standard deviations from three replications.