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The stems of Dendrobium officinale Kimura et Migo (Dendrobii Officinalis Caulis) have a high medicinal value as a traditional Chinese medicine (TCM). Because of the limited supply, D. officinale is a high priced TCM, and therefore adulterants are commonly found in the herbal market. The dried stems of a closely related Dendrobium species, Dendrobium devonianum Paxt., are commonly used as the substitute; however, there is no effective method to distinguish the two Dendrobium species. Here, a high performance liquid chromatography (HPLC) method was successfully developed and applied to differentiate D. officinale and D. devonianum by comparing the chromatograms according to the characteristic peaks. A HPLC coupled with electrospray ionization multistage mass spectrometry (HPLC-ESI-MS) method was further applied for structural elucidation of 15 flavonoids, 5 phenolic acids, and 1 lignan in D. officinale. Among these flavonoids, 4 flavonoid C-glycosides were firstly reported in D. officinale, and violanthin and isoviolanthin were identified to be specific for D. officinale compared with D. devonianum. Then, two representative components were used as chemical markers. A rapid and reliable high performance thin layer chromatography (HPTLC) method was applied in distinguishing D. officinale from D. devonianum. The results of this work have demonstrated that these developed analytical methods can be used to discriminate D. officinale and D. devonianum effectively and conveniently.

In this study, microwave assisted puffing technology was developed to increase the extraction efficiency of polysaccharides from D. devonianum. Fresh stems of Dendrobium devonianum were processed using microwave puffing technology and the processing conditions were explored and optimized to increase the extraction yield of polysaccharides. The effects of sample length (SL), initial moisture content (IMC), microwave power (MP), and processing time (PT) on quality attributes of the products, in terms of expansion ratio and sensory evaluation, were analyzed using response surface methodology. The optimal SL, IMC, MP, and PT were 3.5 cm, 22%, 702 W, and 31 s, respectively, which resulted in optimal expansion ratio and sensory score of 326.1% and 8.63, respectively. Furthermore, the extraction yield of polysaccharides from the microwave-puffed products was increased by 18.9% compared with that from nonpuffed samples. Antioxidant and anti-hyperglycemic activities of polysaccharides from puffed and nonpuffed D. devonianum were also evaluated and compared. Practical applications We developed a novel microwave assisted puffing technology to increase the extraction efficiency of polysaccharides from D. devonianum. Polysaccharides, the major active components of Dendrobium species, exhibit the potential as an inhibitor, including immunomodulator, antioxidant, anti-tumor and anti-hyperglycemic agent.