Array-based techniques for fingerprinting medicinal herbs

Bioactive compounds in certain medicinal herbs affect cell communication and signalling [1], induce inflammatory responses [2] and help prevent diseases [3]. Chinese medicinal herbs such as ginseng (Panax ginseng), Danshen (Salvia miltiorrhiza), Korean Mint (Agastache rugosa), Chinese motherwort (Leonurus japonicus) are globally recognized for treating human disorders. Currently, the global market for medicinal herbs currently is valued over $60 billion a year and growing at an annual rate of 6.4% [4].Development and acceptance of herbal medicine are hindered by misidentification and adulteration of medicinal herbs which may lead to loss of therapeutic potency and potential intoxication [5]. Authentication of medicinal herbs ensures their therapeutic potency.Morphological and histological methods, which have been used for authentication, are subjective and ineffective [6]. Chromatographic fingerprinting (eg HPLC) can be affected by the variations in growing conditions, harvesting periods and processing methods of the herbs [7]. Genomic tools were developed to fingerprint herbal plants as genomic information is more specific and does not readily change with environmental factors. Polymerase chain reaction (PCR)-based techniques, eg random amplified polymorphic DNA (RAPD) [8-10], amplified fragment length polymorphism (AFLP) [11] and sequencing-based techniques based on species-specific sequences, eg internal transcribed spacer (ITS) [12], have also been used to identify herbal species. PCR-based methods are limited by agarose gel electrophoresis which is time consuming and not feasible for large scale genotyping operations [13]. Moreover, some PCR-based methods such as microsatellites and sequence characterised amplified regions (SCAR) require prior sequence information and may not be suitable for fingerprinting the species with poor genomic resources [13,14].DNA microarrays were used to identify medicinal herbs by detecting the hybridisation between fluorescent targ