Catalyzes the conversion of methylthioalkyl glucosinolates into methylsulfinylalkyl glucosinolates. Specific for 8-methylthiooctyl (8-MTO) glucosinolates. a (Z)-omega-(methylsulfanyl)-N-sulfo-alkylhydroximate S-glucoside + H(+) + NADPH + O2 = a (Z)-omega-(methylsulfinyl)-alkyl-glucosinolate + H2O + NADP(+) Increased accumulation of methylthiooctyl glucosinolates in seeds. Belongs to the FMO family.