Composition, radical scavenging and antifungal activities of essential oils from 3 Helichrysum species growing in Cameroon against Penicillium oxalicum a yam rot fungi

The chemical composition of essential oils from leaves of Helichrysum cameroonense Hutch. and Dalziel, Helichrysum cymosum Sensu C. D. Adam, Helichrysum globosum Sch. Bip. ex A. Rich. and flowers of Helichrysum cameroonense was examined by means of GC and GC-MS. In addition, the radical scavenging and antifungal activities were assayed according to the DPPH (Diphenyl Picryl Hydrazyl) and dilution methods respectively. The results showed a predominance of monoterpenes in the oils of the leaves (89.5%) and flowers (62.9%) of H. cameroonense and of sesquiterpenes (58.0%) in that of H. cymosum. Extract from H. globosum was characterized by comparable proportions of monoterpenes (49.6%) and sesqiterpenes (49.1%). The major components were found to be a-pinene (46.4%) and camphor (11.5%) in the oil of leaves of H. cameroonense while a-pinene (31.4%) and guaienol (18.9%) were those from the flowers of the same specie. A-3-Carene (16.1%) and p-caryophyllene (12.0%) were the predominant compounds of the essential oils of H. cymosum and a-pinene (36.6%), valerianone (10.9%) were those of H. globosum. The radical scavenging activities of essential oils from the leaves of H. cameroonense and H. cymosum were found to be 4.9 and 6.3 g/l respectively while butylated hydroxy toluene (BHT) used as reference has a SC50 =7.0 mg/l, On another hand, the essential oils from the leaves of these Helichrysum species showed significant antifungal activities against Penicillium oxalicum, with percent inhibition at 5 mg/mL ranging from 54.7 to 100%. These results highlight the potential of some essential oils as an alternative tool to fight this pathogen which is one of the most prevailing causing agent of soft rot of post harvest yam tuber.