Fruit juice mediated multicomponent reaction for the synthesis of substituted isoxazoles and their in vitro bio-evaluation

A simple, efficient and eco-friendly procedure for the synthesis of isoxazole derivatives (4a–4h) using one-pot three-component reaction between substituted aldehydes (1a), methyl acetoacetate (2a) and hydroxylamine hydrochloride (3a) has been achieved in presence of Cocos nucifera L. juice, Solanum lycopersicum L. juice and Citrus limetta juice respectively. The homogeneity of synthesized compounds was confirmed by melting point and thin layer chromatography. The synthesized compounds were characterized by using (1)H NMR, FTIR and CHN analyses and evaluated for in vitro herbicidal activity against Raphanus sativus L. (Radish seeds). The compounds (4a–4h) were also screened for their fungicidal activity against Rhizoctonia solani and Colletotrichum gloeosporioides. Antibacterial activity was also tested against Erwinia carotovora and Xanthomonas citri. From bio-evaluation data, it was found that compound 4b was most active against Raphanus sativus L. (root) and Raphanus sativus L. (shoot) respectively. Compound 4b was also found most active against both the fungus viz. R. solani and C. gloeosporioides showing maximum percentage growth inhibition i.e. 90.00 against R. solani and 82.45 against C. gloeosporioides at 2000 µg/mL concentration. Compound 4 h has shown maximum inhibition zone i.e. 3.00–9.60 mm against Erwinia carotovora at 2000 µg/mL concentration. Maximum Xanthomonas citri growth was also inhibited by compound 4 h showing inhibition zone 1.00–5.00 mm at highest concentration.