Present work consists of screening of Croton sparsiflorus (Euphorbiaceae), Laggera aurita (Asteraceae) and synthesized benzothiazine derivatives for their xanthine oxidase inhibitory potential. Extraction and bioassay guided isolation of Croton sparsiflorus resulted in the identification of eleven compounds. Three compounds were purified and identified as crotsparinine (8), crotsparine (9) and sparsiflorine (10). Sparsiflorine (10) was the most active XO inhibitor from Croton sparsiflorus with IC 50 value of 18.0 ± 0.4 μM followed by crotsparine (9) and crotsparinine (8). Twelve compounds were also identified from Laggera aurita but only two were purified and subjected to XO inhibition potential namely 2,4-di-tert-butylphenol (21) and 2,4-ditert-butyl-6-nitrophenol (22) with IC 50 values of 43.2 ± 1.9 μM and 40.2 ± 1.2 μM respectively. Both the isolated compounds from L. aurita inhibited XO strongly. Out of thirteen synthesized benzothiazine derivatives twelve contain 1,4- benzothiazine nucleus. This nucleus is quite familiar to natural products. These derivatives were characterized by EIMS, 1 H-nmr and XRD analysis as 2H-1,4- benzothiazin-3(4H)-one (24), 2H-1,4-benzothiazin-3(4H)-one 1,1-dioxide (25), ethyl 4- hydroxy-2H-1,2-benzothiazine-3-carboxylate 1,1-dioxide (27), (3-oxo-3,4-dihydro-2H- 1,4-benzothiazin-2 yl)acetic acid (28), ethyl (3-oxo-3,4-dihydro-2H-1,4-benzothiazin-2- yl)acetate (29), ethyl 3-oxo-3,4-dihydro-2H-1,4-benzothiazine-2-carboxylate (30), ethyl (1,1-dioxido-3-oxo-3,4-dihydro-2H-1,4-benzothiazin-2-yl)acetate (31), 2-(3-oxo-3,4- dihydro-2H-1,4-benzothiazin-2-yl)-N-phenylacetamide (32), N-cyclohexyl-2-(3-oxo-3,4- dihydro-2H-1,4-benzothiazin-2-yl)acetamide (33), 1-(3-methyl-4H-1,4-benzothiazin-2- yl) ethanone (34), ethyl 3-methyl-4H-1,4-benzothiazine-2-carboxylate (35), ethyl (2E)- 2H-1,4-benzothiazin-3(4H)-ylideneacetate (36) and 2-benzoyl-2H-1,4-benzothiazin- 3(4H)-one (37). They showed little to moderate XO inhibition potential with [(3-oxo-3,4- dihydro-2H-1,4-benzothiazin-2 yl)acetic acid (28) as the most active followed by 2H-1,4- benzothiazin-3(4H)-one (24)] { IC 50 values of 124.2 ± 13.9 μM and 212.7 ± 16.4 μM respectively }.