EFFECTS OF HOT WATER TREATMENT ON THE PHENOLIC PHYTOCHEMICALS AND ANTIOXIDANT ACTIVITIES OF LEMON GRASS (CYMBOPOGON CITRATUS)

Cymbropogon citratus (Lemon grass) is widely cultivated in the tropical areas of Africa, America and Asia. It is principally taken as a tea to remedy digestive problems, diarrhea, fever, coughs, elephantiasis, flu, gingivitis, headache, leprosy, malaria, ophthalmia, pneumonia, vascular disorders and stomach ache. A comparative study of phenolic phytochemicals and antioxidant properties of cold water extract (CWE) and hot water extract (HWE) of Cymbropogon citratus has been assessed. Hot water extraction was prepared by boiling Cymbropogon citratus in water at 100 oC for 10 minutes (1:10 w/v) while that of cold extraction was carried out by soaking Cymbropogon citratus in water for 10 minutes (1:10 w/v). The extracts were centrifuged to give clear supernatants that were used for subsequent analysis. The results revealed that CWE (4.3 mg/g) had a significant (P<0.05) higher vitamin C content than HWE (2.7 mg/g) content. Conversely, there was a significant (P<0.05) increase in the total phenol [CWE (0.3 mg/g), HWE (0.5 mg/g)], total flavonoid [CWE (0.2 mg/g), HWE (0.3 mg/g), reducing property [CWE (16.8 mg/g), HWE (34.0 mg/100g)] and ABTS* scavenging ability [CWE (36.6 mM TEAC/100g), HWE (65.0 mM TEAC/100g)]. Also, in a dose dependent manner, HWE showed significantly (P<0.05) higher DPPH radical scavenging ability, Fe2+ chelating ability and OH* scavenging ability than CWE. Conclusively, heat treatment may affect antioxidant properties due to release of phenolic phytochemicals, hence contributing to the health promoting and disease preventing abilities of Cymbropogon citratus.