A study of the antifungal activity of black tea polyphenols (catechin and theaflavin) against candida species

Abstract

Catechin and theaflavin are two polyphenols found in black tea, the latter being a dimer of the former, which is a theogallate. Catechin and theaflavin are obtained from fermented leaves of the tea plant (𝘊𝘢𝘮𝘦𝘭𝘭𝘪𝘢 𝘴𝘪𝘯𝘦𝘯𝘴𝘪𝘴) by the standard extraction method described by Vuataz et al (1959) and Roberts and Smith (1963). Although anti-oxidant, some antifungal and anti-cariogenic properties of both catechin and theaflavin have been reported there has been no report on any anti-candidal activity of these polyphenols in the literature to date.

The objectives of the study are: 1) to verify the antifungal effect of catechin and theaflavin on isolates of five different species of 𝘊𝘢𝘯𝘥𝘪𝘥𝘢; 2) to determine the minimal inhibitory concentration (MIC) of catechin and theaflavin in respect of 𝘊𝘢𝘯𝘥𝘪𝘥𝘢 𝘢𝘭𝘣𝘪𝘤𝘢𝘯𝘴; 3) to determine the existence of post anti-fungal effect (PAFE) if any, of these polyphenols in respect of Cialbicans and 4) to assess the qualitative effect if any on the yeast cells exposed to the polyphenols under study using a scanning electron microscope (SEM).

Both catechin and theaflavin solutions were separately prepared to percentage concentrations of 1.25, 0.625, 0.3125 and 0.156 with sterile distilled water. Five isolates of each of the following five 𝘊𝘢𝘯𝘥𝘪𝘥𝘢 species were used for this study: 𝘊𝘢𝘯𝘥𝘪𝘥𝘢 𝘢𝘭𝘣𝘪𝘤𝘢𝘯𝘴, 𝘊𝘪𝘨𝘭𝘢𝘣𝘳𝘢𝘵𝘢, 𝘊 𝘱𝘢𝘳𝘢𝘱𝘴𝘪𝘭𝘰𝘴𝘪𝘴 𝘊𝘬𝘳𝘶𝘴𝘦𝘪, 𝘢𝘯𝘥 𝘊 𝘵𝘳𝘰𝘱𝘪𝘤𝘢𝘭𝘪𝘴. Antifungal effect of the polyphenols was studied using the standard gel diffusion method. The isolates were inoculated on Mueller- Hinton agar (MHA) plates.l Sul, of one of the four concentrations stated above of either catechin or theaflavin was added to wells bored in the middle of the inoculated area. The plates were then incubated for 24-36 hours at 37° C. The experiment was quadruplicated and repeated on a second day. The inhibitory zones observed were measured using an image analysis software on a camera-linked computer. The MIC was determined only with 𝘊. 𝘢𝘭𝘣𝘪𝘤𝘢𝘯𝘴. It was determined visually and spectrophotometrically at 595nm, following 24 h of incubation at 37°C. Post antifungal effect of both polyphenols was studied using the method described by Ellepola and Samaranayake (1998). 𝘊. 𝘢𝘭𝘣𝘪𝘤𝘢𝘯𝘴 ATCC 90028 was exposed to the MIe of both catechin and theaflavin and the cells were prepared in the standard method for SEM study.

All isolates of all five species were found to be sensinve to both catechin and theaflavin. There was a statistically significant inter-species variation of sensitivity with 𝘊. 𝘨𝘭𝘢𝘣𝘳𝘢𝘵𝘢 being the most sensitive and 𝘊. 𝘵𝘳𝘰𝘱𝘪𝘤𝘢𝘭𝘪𝘴 being the least sensitive with 𝘊. 𝘢𝘭𝘣𝘪𝘤𝘢𝘯𝘴 and other species occupying intermediate positions. The MIC of both catechin and theflavin for 𝘊. 𝘢𝘭𝘣𝘪𝘤𝘢𝘯𝘴 was found to be 0.625%. PAFE was observed with theflavin but a paradoxical effect of post antifungal enhancement was seen with catechin. Under the SEM the exposed 𝘊. 𝘢𝘭𝘣𝘪𝘤𝘢𝘯𝘴 cells showed structural damage in the form of shrivelling and collapse.