Doi: 10. 1016/j chroma

3.5.2. Analysis of saccharides and their derivatives

In order to evaluate the quality of Herba Cistanches comprehensively, galactitol, the main active component with laxative activity in Herba Cistanches [18,19,97,98] has been recently selected as an indicator to evaluate the quality of Herba Cistanches, combining with PhGs. In order to comprehensively evaluate the quality of C. tubulosa from different areas, Cai developed a method of quantitation of glactitol coupled with echinacoside (11) and acteoside (2) by HPLC. ELSD was selected as the detector for galactitol, due to its weak terminal absorption in UV spectrum, and a Prevail Carbohydrate ES polymergel column was used for its separation. Batches of C. deserticola and C. tubulosa from various habitats were measured, and the processing method of fresh C. tubulosa decoction pieces was also optimized by this method [92,93]. Their resultsshowedthatthecontentsofgalactitol,echinacoside(11)and acteoside (2) in the C. tubulosa decoction piece by the described method were several times higher than those dried by insolation or by traditional method [93]. Additionally, Zhang ever established a TLC identification method of mannitol in C. deserticola, using ethyl acetate–pyridine–water (7:2:1) as developing solvent, and 1% KMnO₄ solution as coloring agent [65].
As for the content determination of polysaccharides in Cistanche species, phenol–sulfuric acid is the most frequently used method, and the content of polysaccharides in C. salsa through different extraction methods was determined to be from 11.61% to 13.22% [123–125]. However, those are only some preliminary analytical results due to the limitation of colorimetric method.

3.6. Alkaloids and their corresponding analysis

Up to now, only two alkaloids have been isolated from Cistanche species, that is betaine (65) and N,N-dimethyl glycine methyl ester (66) (Fig. 3) [126]. Betaine (65) is an alkaloid distributed commonly in plants, so there are more reports on its qualitative and quantitative analysis. Zhang compared the content variation of betaine in C. deserticola before and after processing, using a TLC identification combined with colorimetric method [127]. This TLC method was also collected in Chinese Pharmacopoeia 2000 [8], while that quantitation method by colorimetry was later adopted by others to optimize the extraction technology of Herba Cistanches [128,129]. In 2007, Gong reported an HPLC method for the detection of betaine in Cistanche plants coupling with ELSD detector, and betaine had been found to exist only in C. deserticola, but not in C. tubulosa. Thus, the author suggested that betaine should be used as a marker to distinguish these two kinds of Cistanche plants [101]. However, considering that the sample batches are only two for each species, and one of the habitats of C. tubulosa (Yunnan) is uncertain, we recommendedthatthisconclusionshouldbeprovenfurther.Additionally, the TLC identification of betaine for Herba Cistanche has been removed from Chinese Pharmacopoeia since 2005, due to its nonspecific property. Thus, taking it as a sole indicator to optimize the extraction technology of Herba Cistache was not reasonable [129].
3.7. Other compounds
There are small amounts of other compounds, such as phenolic glycosides, monoterpenoids, sterols or their glycosides, fatty acids, amino acids and some trace elements, etc. existing in Cistanche plants [13,41,42,103,105,130–133].