Organosulfur compounds of the general formula (2) are described, wherein R1 and R2 are linear or branched C1- C5 alkyl; linear or branched C1- C5 alkenyl with the proviso that R1 is not prop-1-enyl (allyl); substituted linear or branched C1- C5 alkenyl or substituted linear or branched C1- C5 alkyl, in which the substituents are selected from OR3, NR4R5, COOR6, CONR7R8, in which R3 is selected from H, COR9, para- methoxybenzyl and trialkylsilyl, in which R9 is alkyl or substituted alkyl; R4 and R5 are alkyl or R4 and R5 together form a phthalimido group; R6 is alkyl or substituted alkyl; and R7 and R8 are alkyl or substituted alkyl; substituted or unsubstituted aromatic specifically where R1 and R2 are benzyl, para-methoxybenzyl and/or ortho,para- methoxybenzyl and substituted or unsubstituted heteroaromatic. The compounds can be used for inhibiting the growth of tumour cells and for treating cancer. A pharmaceutical composition and a method of preparing the compounds are also described.