Cyclic Tetrapyrrolic Photosensitisers from the leaves of Phaeanthus ophthalmicus

• Published in: Chemistry Central journal 2011-06, Vol.5 (1), p.32-32, Article 32
• Main Authors: Tan, Pei Jean, Ong, Cheng Yi, Danial, Asma, Yusof, Hirzun Mohd, Neoh, Bee Keat, Lee, Hong Boon
• Format: Article
• Language: English
• Subjects: Biological Chemistry; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Research Article
• ISSN: 1752-153X; 1752-153X
• DOI: 10.1186/1752-153X-5-32

Background Twenty-seven extracts from 26 plants were identified as photo-cytotoxic in the course of our bioassay guided screening program for photosensitisers from 128 extracts prepared from 64 terrestrial plants in two different collection sites in Malaysia - Royal Belum Forest Reserve in the State of Perak and Gunung Nuang in the State of Selangor. One of the photo-cytotoxic extracts from the leaves of Phaeanthus ophtalmicus was further investigated. Results The ethanolic extract of the leaves from Phaeanthus ophtalmicus was able to reduce the in vitro viability of leukaemic HL60 cells to < 50% when exposed to 9.6 J/cm 2 of a broad spectrum light at a concentration of 20 μg/mL. Dereplication of the photo-cytotoxic fractions from P. ophthalmicus extracts based on TLC R f values and HPLC co-injection of reference tetrapyrrolic compounds enabled quick identification of known photosensitisers, pheophorbide- a , pheophorbide- a methyl ester, 13 2 -hydroxypheophorbide- a methyl ester, pheophytin- a and 15 1 -hydroxypurpurin 7-lactone dimethyl ester. In addition, compound 1 which was not previously isolated as a natural product was also identified as 7-formyl-15 1 -hydroxypurpurin-7-lactone methyl ester using standard spectroscopic techniques. Conclusions Our results suggest that the main photosensitisers in plants are based on the cyclic tetrapyrrole structure and photosensitisers with other structures, if present, are present in very minor amounts or are not as active as those with the cyclic tetrapyrrole structure.