natural-products-in-plant-pest-management

Antimicrobials to Prevent Biodeterioration of Grains 99(C 7+ C 8) are mingled together and appeared at δ 7.7 as a multiplet. Thesignal due to the C 3’ and C 2protons appeared at 6.84 and 7.49 as a doublet,respectively.13 C-NMR data of the bioactive compound showed peaks at δ 146.85(C 2),143.8 (C 4), 119.77(C 3), 115.5(C 7), 114.76(C 8), 2 106.3(C 3’), and 99.86 (C 2’), whichare inconsistent with structure.GC–MS analysis showed a molecular ion peak at M/z 186.17 consistentwith the molecular formula C 11H 6O 3. The peak at M/z 158 was due to theformation of the coumarin cation. The recorded chromatogram of the plotmatched with the chromatogram of an already known compound, 2H-furo[2,3-H]-1-benzopyran-2-one. Figure 4.4 presents the molecular structure of thebioactive compound.In vitro evaluation of the antifungal active componentTen species of Aspergillus, viz. A. flavus, A. niger, A. terreus, A. tamarii, A. flavusoryzae, A. fumigatus, A. candidus, A. ochraceous, A. flavipes and A. flavus columnaris,and two species of Penicillium, viz., P. chrysogenum and P. notatum, isolatedfrom maize seeds and known to cause biodeterioration of grains served as testfungi for the antifungal activity assay using the poisoned food technique.The poisoned food technique is as follows. Malt extract salt agar (MESA)medium amended with different concentrations of the bioactive compoundwere prepared and poured into sterile Petri plates and allowed to cool andsolidify. Mycelium discs (5 mm diameter) of 7-day-old cultures of species ofAspergillus and Penicillium were placed at the centre of the plates and incubatedat 25 ± 1°C for 7 days. The MESA medium without the bioactive compoundserved as a control. The colony diameter was measured. Similarly the fungicidesCaptan (C 9H 8Cl 3NO 2S) and Thiram (C 6H 12N 2S 4) were also tested againstall the test fungi at the recommended dose of 2000 ppm concentration for comparativeevaluation. The percentage inhibition of mycelial growth if any wasdetermined by the formula PI = C – T/C × 100; where C is the diameter of controlcolony and T is the diameter of treated colony (Pinto et al., 1998). MICs foreach of the test fungi were determined on the basis of the concentration neededto inhibit totally the test fungi (Fig. 4.5).The total inhibition of A. flavus was observed at 100 ppm. A. niger andA. fumigatus were totally inhibited at 500 and 600 ppm, respectively. A. flavusoryzae and A. flavus columnaris were totally inhibited at 700 ppm. A. ochraceousand A. flavipes were totally inhibited at 900 ppm. Total inhibition ofOOOFig. 4.4. Molecular structure of the bioactive compound, 2H-furo [2,3-H]-1-benzopyran-2-one, isolated from seeds of P. corylifolia.