Investigation of free radical scavenging activity by ESR for coumarins isolated from Tecoma radicans

Tecoma radicans (Campsis radicans (L.) Seem.), F. Bignoniaceae is a species that belongs to a tropical family but has been introduced in many countries as ornamental. Phytochemical investigation of the aerial parts of Tecoma radicans (L.) DC, indicates the presence of four coumarins, 2', 3'-epoxide alloimperatorin (I), pabulenone (II), pereflorin B (III) and 17–methylbothrioclinin (IV). One chromone was also isolated peucenin–7-methyl ether (V), and showed the violet colour with FeCl3 directly while the four coumarins showed this violet after alkalinization with ammonia solution. They were isolated, purified and identified from their spectroscopic analysis and comparing with the published data [1]. When successive extracts of T. radicans and coumarin fraction were screened for cytotoxic activity in concentration of 100µg/0.1 mL DMSO, in vitro using a single tumour (Ehrlich ascites carcinoma cells) [2], they showed no cytotoxic activity. When the coumarin fraction and isolated compounds were examined for free radical scavenging activity, using the stable DPPH free radical [3] and recorded by ESR, using vitamin C as control, it was found that the whole coumarin fraction was the most active, Fig.1, (89. 06% inhibition of DPPH free radical), and the isolated components are 0, 25.9, 8.45, 13.85 and 50% respectively, Table 1.