Preservatve Potentials of Datura metel Seed Oil on Triplochiton scleroxylon Wood (Schumann) against Fungal Attack

: This experiment was carried out to evaluate the potential of extracted Datura metel seed oil as a bio wood preservative against fungi attack as reports have shown bio-preservatives to be toxic free and environmentally friendly. The oil was extracted from the seed by Soxhlet apparatus using N-Hexane and ethanol solvents and using volume-to-volume method of dilution kerosene (at 50%) was added to increase its quantity thereafter. The phytochemical screening of the seed of Datura metel revealed the presence of tannins, alkaloids, flavonoids, saponins and phenols. Wood samples of Triplochiton sceleroxylon were cut to 20 × 20 × 60mm and the dimensioned wood samples were soaked for 72 hours in the seed oil extract hence preservative absorption rate and percentage weight loss of wood was determined on exposure to a purely cultured Sclerotium rolfsil (brown rot fungi) and Pleurotus ostreatus (white rot fungi). Data obtained were subjected to analysis of variance at α0.05 and the results showed the highest value of mean weight loss of 18.29% while the samples exposed to brown rot fungi has a mean value of 14.12% and white rot a lowest mean value of 12.72%. The highest absorption was observed to be 92.73 kg/m at 100 % concentration level of D,metel extract. Based on the results obtained, the seed-oil extracts of Datura metel have the potential of being an effective wood preservative.

Wood is a natural organic fibrous tissue comprising of cellulose embedded in a matrix of Lignin, materials which are a combination of simple sugars that can biodegrade. It has always been a pre-eminent construction material for both domestic and industrial uses as much as up to 80% in Nigeria (Ogbogu,1996), thus the need to preserve them. Notwithstanding, wood can be unusable due to fungal infestations, insect attacks, fire attacks and also mechanical failure (Areo, 2002). Some timbers have highly valued properties of excellent resistance to various agents of deterioration and are therefore termed highly durable, while many others have only moderate resistance or no resistance to insect and fungi attacks, hence, wood preservation becomes a necessity (FAO, 1986). Consequently, only durable wood species are being selected and exploited for structure and construction purposes (Oluwafemi and Adegbenga, 2007). However, some work of literatures have revealed that there are other wood species of low durability that can still be used for construction purposes if properly treated, thus corroborating. Makpa (1998) who stated that for wood can give optimum satisfaction in service if it must undergo preservation. Also, Falemara et al., 2014 reported that wood treated with the appropriate preservative increases its service life. Wood preservatives are pesticides that protect wood against the attack of bio-deteriorating agents like insects, fungi or bacteria. Many chemical preservatives have been found useful against fungal and insect attacks (Ahmed et al., 2010), however, their toxic properties and poor degradability of have been reported to cause harmful effects to consumers and the environment (Adetogun, 1998;Onuorah, 2000). This therefore calls for a need to develop environmentally friendly biological preservatives that will serve as alternatives to the hazardous synthetic ones.
Datura metel is a shrub-like perennial herb which grows in the wild, it is commonly known as devil*s trumpet and known worldwide for its chemicals and ornamental use. The previous studies on the extracts of the leaves of D. metel showed that it contained biopreservative agents. (Donatus andEphraim, 2009), Hossain et al., (2014) found many phytochemicals such as alkaloids, flavonoids, phenols, saponins, sterols and tannins in the leaf, and findings from (Alabri et al., 2014;Roy et al., 2016) and (Hossain et al., 2014, suggests that D. metel extract possess antioxidant and antibacterial, respectively. Also, it was opined that it contained antifungal (Akharaiyi et al.,2011), anti-proliferative (Rajesh and Sharma, 2002;Dabur et al.,2005), and immunosuppressive properties (Bellila et al., 2011;Yang et al., 2014). However, little information is available about the biopreservative agents in the seed oil of Datura metel and its efficacy for treating wood. Triplochiton scleroxylon commonly known as obeche belonging to the family of sterculiaceae, is a large deciduous forest tree and a well-known specie in the wood industry, and its wood is moderately durable. Therefore, objective of this study is to determine the preservative potential of Datura metel seed oil on Triplochiton scleroxylon wood against fungal attack.

MATERIALS AND METHODS
Preparation of Datura metel Seed Oil: Ripe fruits of Datura metel were sourced in large quantities and depulped to separate the seeds, it was later dried within shade and then oven dried at 40 C for about 48 to 72 hrs and ground into powder in a blender. The oil was extracted chemically from the ground and sieved (1mm mesh) seeds with N-hexane and ethanol in Soxhlet apparatus using about 32g of the powdered seed and 350 mL of solvent over a period of 8hrs. Subsequently, the solvent was kept off using rotary evaporator at 40 C under reduced pressure. Seed oil was then collected in capped tubes and refrigerated at 4 C for further study. The procedure was replicated and the extracted oil was stored in a covered bottle prior its use.
Phytochemical Screening of Datura metel Seed: The Phytochemical screening of was done following the standard procedure by (Brain and Turner, 1976) on the seeds for the presence and amount of tannins, alkaloids, flavanoids, saponins and phenols.
Preparation of test fungi: The brown and white fungi used for this study was obtained from International Institute of Tropical Agriculture laboratory, Ibadan using potato dextrose agar as a culture medium.

Preparation of Test Fungicide:
The volume-tovolume method was used for the preparation of different concentration levels of the oil extract using kerosene as the diluent (Ajala et al., 2014). This implies that, 0mL of D.metel seed oil in 100 mL of Kerosene (diluent) is equivalent to 0% dilution and 100 mL D.metel seed oil in 0 mL kerosene is equivalent to 100 % respectively while the untreated sample is represented as control. For each concentration, ten replicates were used for each oil treatment which was thereafter separated into five replicates for the fungi.
Preparation of Culture Medium: A nutrient medium of Potato Dextrose Agar (PDA) in distilled water was prepared. 40 mL of the PDA was poured into McCartney bottles and sterilized by autoclaving at 0.1 N/mm2 (120 °C) for a period of 20 minutes. The medium was inoculated with the test fungi 6 days after preparation of the bottles (Sarker et al., 2006).

Innoculation of Test Blocks:
The wood blocks were infected by placing them in the bottles in which there were actively growing cultures of the test fungi such that they came in contact with the aerial mycelium of the fungus. The control test blocks were wrapped in aluminum foil and sterilized in the oven before introduction to the test fungi, it was then incubated at room temperature (27 ± 2 o C) in the laboratory for 14 weeks.

Treatment of Test Blocks:
The properly identified and tagged wood samples were cut to into standard sizes (20 x 20 x 60 mm) dried in the oven at 103 0 C for 24hrs to remove the moisture and weighed. Soaking method (FAO, 1986) was used to treat the wood test blocks with the preservatives. They were completely immersed in the bio-preservative for 72 hours. The wood blocks were conditioned and treated with various concentrations of castor oil (0 mL, 20 mL, 40mL, 60 mL, 80ml and 100 mL) so as to obtain maximum absorption, while the others were left unsoaked to serve as control for both treatments. They were removed and air dried for three days and then weighed (W3).The absorption rate was calculated using equation (1)  (2) Where W1 = Weight after absorption; W2 = Weight after exposure to fungi Data Analysis: Data obtained were subjected to analysis of variance (ANOVA) for the significant difference that exist between treatments on the wood samples based on the absorption rate and weight loss used while comparison of means was conducted, while comparison of means was conducted using Duncan Multiple Range Test (DMRT) to identify which groups were significantly different at α 0.05.The experimental design adopted for this study was a completely randomized design (CRD).

RESULTS AND DISCUSSION
attracts and deters insects and have also been reported to have antimicrobial properties which are effective against fungal growth (Carson and Hammer, 2010) are also present in the oil. Flavonoids which are phenolic structures found abundantly in photosynthesizing cells and are so important a plant component due to their active hydroxyl groups and anti-oxidative and antimicrobial properties (Güder et al., 2014) are also found to be present in the oil. They are also known to have anti-inflammatory and antitumor activity and have also been reported to inhibit wood decay fungi (Onuorah 2000;Yen et al., 2008;Tumen et al., 2013;Li et al., 2014), previous studies have reported that quantification of phenolic compounds in plant extract is influenced by the chemical nature of the extraction solvent (Kumaran et al. 2007 ). Saponins which are also a major family of secondary metabolites that occur in a wide range of plant species (Osbourn 1996) produced by plants as a defensive mechanism to stop attacks by foreign pathogens, which makes them natural antibiotics (Okwu and Emenike, 2006) have also been reported to be present in the oil. They are also responsible for biological activity against insects hence they are involved in plant disease resistance because of their well-known antimicrobial activity (Papadopoulou et. al, 1999;Bouarab et.al, 2002;Wittstock andGershenzon, 2002, Elisa et.al, 2007). Terpenoids used as flavoring agents, insect repellents, fungicides and medicinal purposes (Johnson and Morgan, 1997) are also found to be present in the seed oil. Several other research works (Singh and Sushilkumar 2008;Sotannde et al. 2011;Djenontin et al. 2012;Addisu et al. 2014;Faruwa et al. 2015) have also reported the efficacy of plants extractsas bio-preservative against fungi and termite attacks. Mazhar et al., (2013) affirmed that the seed extracts of medicinal plant offers a source of naturally occurring chemicals that could be used because of the repellent, anti-feedant or toxic effects on micro-organisms in feeding assays (Ahmed et al. 2007.  (Okanlawon et al., 2020) which could also be attributed to variations in physical and anatomical characteristics of Triplochiton scleroxylon wood specie and also probably due to the wood of C. petandra being lighter, softer in texture and lower in strength and coarser (Gibbs and Semir, 2003). The wood samples were easily impregnated with D.metel seed oil extract without difficulty due to low viscosity of the extract influenced by viscosity of the diluents which agrees with the work of Adetogun (2011).  Table 3 represents the weight loss of T. scleroxylon due to fungal attack which ranged from 10.04 -38.48 and 11.92 -42.58 for white rot fungi and brown rot fungi respectively. The table also shows the untreated wood samples (control) of T. scleroxylon had the highest value for weight loss (42.58) brown rot and (38.48) white rot respectively which is an indication that the level of attack of untreated wood samples by the fungi is significantly different (higher) to that of the treated samples. The results obtained in this study is in line with the report of Wong and Cheok (2001) who reported that unprotected wood can be attacked by wood deteriorating agents and if this is not controlled can lead to deterioration, loss of structure, extra cost of replacement and even the loss of lives in severe cases. The significant difference in the values obtained for treated and untreated wood samples (control) showcased a reduction in the deterioration of the treated samples thus indicating the effectiveness of the seed oil extract on the treated samples as against the untreated samples (control) and this can be attributed to some varying array of chemical compounds in the seed oil as reported earlier in this study and several other studies (Lukmandaru, 2011;Namujehe and Orikiriza, 2013. Quite a number of studies have also proved the effectiveness of seed oils originated from plants as bio preservatives (Okanlawon et al., 2020a, Okanlawon et al., 2020b, Adegoke et al.2015, Osman et al., 2007. Though there is no significant difference in the weight loss of the wood blocks at 100 mL concentration level for both fungi, the result shows the brown rot to be more virulent in their attack than the white rot fungi which does not agree with the findings of Ajala et al. (2014) who reported that white rot fungi were more virulent than brown rot fungi. The results further shows that level of attack was minimal at higher concentration level of the seed oil extract (80mL and 100 mL) for both fungi which may be due to higher concentration of the oil having a higher quantity of phytoch emicals. Conclussions: Based on the results obtained from this study, it can be concluded that Datura metel seed oil has the potential of being a good bio-preservative especially for Triplochiton scleroxylon wood specie and as an alternative to the non-ecofriendly synthetic wood preservatives .This helps in increasing the service life span of the wood specie, though other methods of application can be further be investigated upon.