EFFICACY OF EXTRACTS OF Datura metel L. AND Euphorbia hirta L. AS PRESERVATIVES FOR BAMBOO (Bambusa vulgaris) AGAINST INSECT AND FUNGI ATTACKS

Abstract

Lignocellulosic materials are susceptible to bio-degradation. Therefore, preservatives are used to enhance their durability for various applications. The toxic nature of synthetic preservatives is encouraging the use of bio-preservative. Bio-preservatives from lignocellulosic extracts though a viable alternative are neither readily available nor their efficacy fully known. This study was therefore designed to evaluate the efficacy of extracts of Datura metel (Dm) and Euphorbia hirta (Eh) as bio-preservatives for Bambusa vulgaris (Bv) against termite and fungi attacks as well as its effect on the laminated board strength. The Dm, Eh and Bv samples were sourced in Ejiooku, Akinyele Local Government, Ibadan, Nigeria, and authenticated in Herbarium of the Forestry Research Institute of Nigeria. Phytochemical screening and characterisation of the extracts were determined by gas chromatography and mass spectrometry. Chemical constituents of the extracts were determined using AOAC procedures. Bio-preservatives were formulated from extracts at 0, 25, 50, 75 and 100% concentrations using ASTM procedures. The Bv culms were sampled from top, middle 1, middle 2 and base, cut into strips (60×20×4 mm) and soaked in the preservatives for 72 hours. Treated samples and control were sub-divided into A, B and C groups. Group A was subjected to termite (Macrotermis bellicosus) attacks for 12 months, while groups B and C were subjected to brown (Sclerotium rolfsii) and white rot (Pleurotus florida) fungi for 6 months in accordance with ASTM procedures. Weight Loss (WL) analyses were done to evaluate the potency of the formulated bio-preservatives, while its effect on gluability of Bamboo Laminated Block (BLB) were also investigated using ASTM procedures. Data were analysed using descriptive statistics and ANOVA at α0.05. Flavonoids (0.11 and 0.12 mg/g), saponins (0.31 and 0.28 mg/g) and tannins (0.04 and 0.03 mg/g) were obtained from Dm and Eh, respectively. Bicyclo [3.1.1] heptanes, 2, 6, 6-trimethyl (1α, 2β, 5α) were major chemical constituents in the two extracts. The presence of these metabolites and chemical constituents formed the basis for their utilisation as preservatives. The WL in group A ranged from 0.62±0.29 to 0.83±0.50 and 0.77±0.40 to 0.96±0.61 for Dm- and Eh-treated samples, respectively, indicating that treated samples resisted termite attack better than control (1.75±0.57). The group B WL ranged from 1.22±0.42 to 1.89±0.33 and 0.76±0.58 to 1.86±0.69 for Dm and Ehtreated samples, respectively. Those of group C ranged from 0.16±0.08 to 0.81±0.51 and 0.28±0.24 to 0.71±0.33 for Dm and Eh-treated samples, respectively. This implied that treated samples were adequately protected against brown and white rot fungi attack compared to control. There were significant variations in WL from top (1.89±0.33) to base (1.25±0.40), showing that fungi attacks were least at the base and highest at the top. Shear strength for BLB ranged from 6.06 to 3.85 N/mm and 5.13 to 4.44 N/mm for control and treated samples, respectively, indicating the suitability of the preservatives as there were no significant differences. The bio-preservatives formulated from Datura metel and Euphorbia hirta extracts offered adequate protection to bamboo against termite and fungi attacks. They are suitable preservatives for lignocellulosic materials.