Acute oral toxicity and antimalarial studies of 7-[(7-methoxy- 4,5-dihydro-1H-benzo[g]indazol-3-yl)carbonyl]-2-phenyl- 5,6,7,8-tetrahydropyrazolo[1,5-a]pyrido[4,3-d]pyrimidin-9 (1H)-one in mouse models