Antioxidant, anti-proliferative and cyclooxygenase-2 inhibitory activities of ethanolic extracts from lemon balm (Melissa officinalis L.) leaves

Antioxidant, anti-proliferative and cyclooxygenase-2 (COX-2) inhibitory activities of ethanolic extracts from freeze (EF) and hot air (EH) dried lemon balm (Melissa officinalis L.) leaves were evaluated. Phytochemical contents in the extracts were also determined. Hot air drying significantly lowered phytochemical contents and biological activities of the extract of lemon balm leaves as compared with freeze drying. EF had higher levels of phenols, phenolic acids, flavonoids, proanthocyanidins, ascorbic acid and gamma-tocopherol than EH. Rosmarinic acid was the major compound and hesperetin was the highest level of flavonoid in the extracts. EF also presented higher antioxidant (beta-carotene bleaching inhibition, scavenging 2, 2-diphenyl-1-picrylhydrazyl radicals, reducing power and Trolox equivalent antioxidant capacity), anti-proliferative (proliferative inhibition for Hep G2, KB and TSGH 9201 human cancer cells) and COX-2 (induced by 12-O-teradecanoylphorbol-13-acetate in KB cells) suppressing activities than EH. The ethanolic extracts of lemon balm leaves, especially EF, may have the potential for cancer chemoprevention. (C) 2012 Elsevier Ltd. All rights reserved.