Comparison of methods to extract PCR-amplifiable DNA from fruit, herbal and black teas

The success of polymerase chain reaction (PCR) assay depends on template deoxyribonucleic acid (DNA) being sufficient with respect to both quantity and quality. Some biological materials contain compounds which inhibit the functioning of DNA polymerase and thus need to be removed as part of the DNA extraction procedure. The aim of the present experiments was to optimise the process of DNA isolation from various types of black, fruit and herbal teas. A comparison was made between two cetyltrimethylammonium bromide (CTAB)-based protocols and two commercially available DNA purification kits. The yield and integrity of the extracted DNA were monitored both spectrophotometrically and using agarose gel electrophoresis. The presence/absence of inhibitors in the DNA preparations was checked by running quantitative real-time PCRs. The optimal protocol was deemed to be the CTAB method described in ISO 21571:2005, so this method is recommended for the routine sample analysis of tea products.