In Vitro Antifungal Activity of Cat’s Claw (Dolichandra unguis-cati L.) on Fungal Contaminants of Grapes
Gisselle Apud, Pedro Aredes-Fernandez,* Diego Sampietro, Marta Vattuone, and Cesar Catalan
*Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Facultad de Bioquímica Química y Farmacia, Universidad Nacional de Tucuman, Ayacucho 471, San Miguel de Tucuman, Tucuman 4000, Argentina
Black rot is a disease caused by Aspergillus species, mainly Aspergillus niger and A. carbonarius. These fungi reduce the yield and quality of grapes. Wine made with rotted fruit has inferior chemical and sensory properties. Synthetic fungicides are commonly used to control Aspergillus species, but have several adverse effects that make their use problematic. This work evaluates the in vitro antifungal activity of plant parts of Dolichandra unguiscati on growth of Aspergillus niger and A. carbonarius. Fractions were obtained from the plant leaves or stems by sequential extraction with dichloromethane (fCh2Cl2), ethyl acetate (fAcet), and methanol (fMeOH). They were assayed on conidial suspensions of A. niger and A. carbonarius by the microdilution method in YES semiliquid medium (2500 to 2.4 ppm). The concentration of the fractions required to inhibit 50% of fungal growth (IC50) were calculated by probit analysis. Dot-blot bioautographies were carried out to establish the minimum inhibitory dose of fungal growth (MID). The composition of the most inhibitory fraction was preliminarily investigated by TLC and the antifungal constituents were detected by TLC bioautography. The fCh2Cl2 fraction from stems showed the most antifungal activity, with IC50 values of 1025 and 1066 ppm and DIM values of 625 and 1250 µg on A. carbonarius and A. niger, respectively. TLC bioautographies indicated an inhibitory activity associated with bands observed at Rf = 0.70 and Rf = 0.63 in the chromatograms observed under UV254nm. Further research is needed to separate and identify these antifungal compounds.
Funding Support: CONICET – Project PIP 2014-627 and ANPCYT – Project PICT 2012-0283