Methodology Technology

2.4 Technology

The goal of molecular pharmacognosy is to solve the problems about medicinal materials to ensure safety, efficacy, and quality of traditional medicines. There are a number of methods involved in molecular pharmacognosy study.

Identification is the first task of molecular pharmacognosy. In the past, identi fication of Chinese medicinal material was mainly based on morphological features. The identification of morphological features is simple and inexpensive but heavily depends on the experience and judgment of the inspector. Then the method of microscopic features identi fi cation has been developed. This method is based on microscopic features, such as texture, tissue arrangement, and cell components.

Other identi fi cation methods also have been developed by physical and chemical ways. These methods provide a more objective, standard, and accurate way for Chinese herbs’ identification than the subjective judgment of inspector based on morphological features of medicinal materials.

One of the most reliable methods for identi fi cation of Chinese medicinal materials is by analyzing DNA. In terms of the mechanisms involved, DNA methods can be classi fi ed into three types, namely, polymerase chain reaction (PCR)-based, hybridization-based, and sequencing-based methods.

2.4.1 PCR-Based Method

PCR-based methods use ampli fi cation of the region(s) of interest in the genome; subsequent gel electrophoresis is performed to size and/or score the amplification products. PCR-based methods include PCR-restriction fragment length polymorphism (PCR-RFLP), random-primed PCR (RP-PCR), direct amplification of length polymorphism (DALP), inter-simple sequence repeat (ISSR), ampli fi ed fragment length polymorphism (AFLP), and directed ampli fi cation of minisatellite-region DNA (DAMD). Except PCR-RFLP and DAMD, these methods are suitable for Chinese medicinal materials which lack DNA sequence information, as they do not require prior sequence knowledge [ 40 ] .

2.4.2 Hybridization-Based Methods

Nucleic acid hybridization is a process in which two complementary single-stranded nucleic acids anneal into a double-stranded nucleic acid through the formation of hydrogen bonds. The most obvious advantage is that if the probes are oligonucleotides shorter than 100 bases, hybridization is possible even after a considerable level of DNA degradation [ 41 ]. However, a relatively large amount of DNA is required and the process is time-consuming (because the hybridization step typically requires overnight incubation) [ 41 ] .

2.4.3 Sequencing-Based Methods

DNA sequences can be used for studying phylogenetic relationships among different species [ 42 ]. Another advantage of using sequencing for species identi fi cation is that the identities of adulterants can be identified by performing sequence searches on public sequence databases such as GenBank. However, prior sequence knowledge is required for designing primers for amplifi cation of the region of interest [ 41 ] .