Aqueous extract from the leaves of purple Peristrophe bivalvis (L.) Merr. give lovely red and purple colours shades with good fastness properties. Chemical investigation of the purple colour aqueous extract (PAE) from aerial parts of P. bivalvis growing in Dong Thap province led to the isolation and structural elucidation of two new phenoxazine alkaloids named perisbivalvine A and perisbivalvine B (N-deacetyl perisbivalvine A) besides the known peristrophine. Their structures were elucidated on the basis of FT-IR, HR-ESI-MS and NMR including HSQC, HMBC spectroscopic data. Considering the widespread utilization as food dyestuff, the authors evaluated the acute oral toxicity of the PAE. The acute median lethal dose in mice (LD50) of the PAE was 26.50 + or - 1.56 g/kg body weight.