Antifungal, Nematicidal and Antioxidant Activity of the Methanol Extracts Obtained from Medicinal Plants

Abstract The nematicidal, antifungal and antioxidant activitiesof methanol extracts from six Vietnamese native medicinal plantswere evaluated by various assays in vitro. Of the plant extractstested, Terminalia nigrovenulosa was found to possess the highestactivity when compared to the others. The leaves and bark of T.nigrovenulosa showed strong inhibitory activity against Meloidogyneincognita and Fusarium solani. The DPPH (1,1-Diphenyl-2-picryl-hydrazyl) radical scavenging, reducing power and totalantioxidant activities of T. nigrovenulosa bark were higher thanthat of the remainder plant extracts. Chitinase activity of theseplants was also investigated using SDS-PAGE. The resultsobtained in the present study indicate that T. nigrovenulosa leafextracts are the greatest potential source as nematicides andfungicides for the control of M. incognita and F. solani. Inparticularly, T. nigrovenulosa bark extracts could be used as apotential source of commercially viable levels of natural antioxidant.Keywords Fusarium solani · medicinal plants · Meloidogyneincognita · methanol extracts · Terminalia nigrovenulosaIntroductionThe control of plant diseases depends primarily upon theapplication of chemicals. However the high costs, non-availabilityat the time of need and the hazards they pose as environmentalpollutants discourage most potential users (Pandey et al., 2000;Elbadri et al., 2008; Harish et al., 2008). Hence, it has becomeimportant to identify alternative control strategies that are aseffective as synthetic pesticides, safe for farmers, consumers, andthe environment and are relatively easily available at a low cost(Fernandez et al., 2001). Several plants have more environmentallyand toxicologically safe selective and efficacious nematicidalpotential (Javed et al., 2006; Dawar et al., 2008). These pesticidesare generally considered to be non-persistent under field conditions,as they are readily transformed by light, oxygen, or microorganismsinto less toxic products. Therefore, fewer residues are expectedfrom those products (Ujvary, 2001; Akhtar et al., 2008). Medicinal plants can provide potential alternatives to the use ofsynthetic pesticides, because they degrade to non-toxic products,and have fewer side effects to non-target organisms and theenvironment. Additionally, such agents often act at multiple andnovel target sites, thereby reducing the potential of plant-parasiticnematodes becoming resistant to it (Isman, 2000; 2006). Medicinalplants have been used in traditional medicine as diuretics, topicalanti-inflammants, and haemostatics (Burt, 2004). Medicinal plantsusually produce many natural products, such as phenols, flavonoids,quinons, tannins, alkaloids, saponins, sterols, and volatile essentialoils. These secondary metabolites have various functions, includingantimicrobial, insecticide and appetite suppressant properties(Wilson et al., 1997; Isman, 2000; Liu and Zhang, 2004; Mares etal., 2005; Soylu et al., 2006; Yazaki et al., 2008; Akhtar et al.,2008). Plants in the genus Terminalia, family Combretaceae,comprising of some 250 species, are widely distributed in tropicalareas of the world (Fabry et al., 1998). A methanol extract ofTerminalia arjuna bark showed nematicidal activity againstHaemonchus contortus (Bachaya et al., 2009). Also, ethanolextract of T. chebula fruit was toxic to both Meloidogyne spp. andCephelobus litoralis (Zia ul Haq et al., 2010). In this study, we focused on 1) the initial assessment of thenematicidal and antifungal activity against the phytopathogenicnematode (Meloidogyne incognita) and fungi (Phytophthoracapsici, Fusarium solani, Fusarium oxysporum and Rhizoctoniasolani) and 2) the determination of antioxidant (DPPH (1,1-Diphenyl-2-picryl-hydrazyl) scavenging, reducing power and total