Biological Activity of <i>Syzygium aromaticum</i>and <i>Ravensara aromatica</i>Essential Oils from Madagascar and Their Possible Use against Postharvest Mango Anthracnose

The fungitoxicity of five Malagasy essential oils (Eos) against Colletotrichum asianum was assessed in terms of conidial germination and mycelial growth. Their effect on defense-related compounds content, physicochemical properties and anthracnose lesions in mango fruits was also determined. Four of the tested Eos were from Ravensara aromatica leaves, and the last Eo was extracted from clove leaves. Their chemical compositions were then determined through GC-MS analysis and the active compound of the most fungitoxic Eo was determined by testing the toxicity of its major component to C. asianums spore germination, mycelial growth and its ability to inhibit anthracnose development on mango fruits. The R. aromatica Eos tested were fungistatic to C. asianum, whereas clove Eo was fungitoxic and the 4 chemotypes of R. aromatica Eo exhibited variable inhibiting capabilities: 1) all tested doses of all Eos (112.5 and 225 μL/L of air) were effective against C. asianum mycelial growth (10% - 100% inhibition) but doses of 225 μL/L were more inhibitory than those of 112.5 μL/L, 2) Conidial germination was more resistant to Eos toxicity since only 225 μL/L of methyl eugenol chemotype of R. aromatica Eo, all tested doses of the sabinene chemotype of R. aromatica Eo and clove Eo were found inhibitory toward conidial germination of C. asianum. 30 μL/L of sprayed clove Eoweretested on inoculated mangoes and were found to be effective against anthracnose development without affecting the resorcinol content in mango peel and the physicochemical properties of mango pulp. Tests on the major components of clove Eo showed fungitoxic activities against mycelial growth and conidial germination of C. asianum similar to those of clove Eo.

Isolation and Identification of Cardenolide Compounds of Gomphocarpus sinaicus and Their Fungicidal Activity Against Soil Borne and Post Harvest Fungi

This study was undertaken to explore new antifungal compounds from the methanolic extract of G. sinaicus. Two cardenolide compounds were isolated and identified by GC-MS as cardenolide glycoside, 15-hydroxy-3,4,5,6-dehydrocalotropin and cardenolide genin, 3,4,5,6-dehydrocalotropagenin. The antifungal activity of these compounds was assessed. Results revealed that both compounds showed pronounced fungicidal activity against both soil borne fungi, R. solani, F. oxysporium, and postharvest fungi, R. stolonifer, P. digtatum, compared to the standard fungicides, flutolanil and copper oxychloride, respectively. The ECs0 values of the cardenolide genin were 0.703, 13.63 and 4.22, 8.403 lag/mL forR. solani, F. oxysporium andR. stolonifer, P. digtatum respectively. On the other hand, the ECs0 values of the standard fungicide, flutolanil, were 9.49 and 61.22 ~tg/mL against R. solani and F. oxysporium. While the ECso values of copper oxychloride were 279.94 and 187.13 p.g/mL against R. stolonifer and P. digtatum, respectively. The results showed that cellulase, PME, PPO of the tested fungi was more sensitive than to cardenolide genin. The strong antifungal activity of cardenolide genin reported in this study indicated that has a potential to be used as fungicides.