Doi: 10. 1016/j chroma

3. Non-volatile compounds

The non-volatile compounds of Cistanche plants mainly include phenylethanoids, iridoids, lignans, alditols, oligosaccharides and polysaccharides. Up to now, more than 100 non-volatile compoundshavebeenisolatedfromCistancheplants.Thedistributionof various type of compounds in Cistanche plants is listed in Table 2. In 1995, Moriya [27,28] reported that the plant material of C. salsa had been wrongly identified before, when he investigated the sources of Herba Cistanches from the Japanese medical markets, so the chemical constituents isolated from C. salsa in the 80s have been reassigned to C. deserticola in this review.

3.1. Phenylethanoid glycosides

3.1.1. Chemical structures of PhGs

PhGs have been regarded as the major active components of Cistanche species. To date, 34 PhGs have been isolated from Cistancheplants,including22disaccharideglycosides,10trisaccharide glycosides and 2 monosaccharide glycoside (Table 3). By analyzing the structures of PhGs in Cistanche, the following structural characteristics have been summarized: the sugar moiety of disaccharide glycosides consists of glucose and rhamnose, with a Glc (3→1) Rha linkage. The glucose commonly links directly with the aglycone, and in its position of C4 or C6, where a coumaroyl or caffeoyl is usually located. When the PhG is to be a trisaccharide glycoside, an additional glucose or rhamnose usually appears at C6 position of the inside glucose. Among those PhGs from Cistanche species, crenatoside (34) is an exceptional one, for an ether ring exists between the position of aglycone and C-2 position of the insideglucoseinitsstructure[34].Recently,theX-raysingle-crystal structure of salidroside (15), a PhG isolated from C. deserticola, has been reported for the first time [44].
ThepharmacologicalactivitystudiesofPhGshavedemonstrated that they have various functions, such as antioxidation, neuroprotection, enhancing immune and sexual function, hepatoprotection,

Table 3 Phenylethanoid glycosides from Cistanche species Compound name R1a R2a R3a R4a R5a R6a R7a Species^b Ref. 2-Acetylacteoside (1) Ac Rha Cf H OH OH H Cd, Cp, Ct, Csa [29–32,47] Acteoside (2) H Rha Cf H OH OH H Cd, Cp, Ct, Csa [30–34,47] Cistanoside A (3) H Rha Cf Glc OMe OH H Cd, Ct [30,33,35] Cistanoside B (4) H Rha Fr Glc OMe OH H Cd [33,36] Cistanoside C (5) H Rha Cf H OMe OH H Cd, Csa [29,36,47] Cistanoside D (6) H Rha Fr H OMe OH H Cd, Csa [29,47] Cistanoside E (7) H Rha H H OMe OH H Cd [37] Cistanoside G (8) H Rha H H H OH H Cd [38] Cistanoside H (9) Ac Rha H H OH OH H Cd [36,39] Decaffeoylacteoside (10) H Rha H H OH OH H Cd, Ct [32,39] Echinacoside (11) H Rha Cf Glc OH OH H Cd, Cp, Ct, Csa [30–33,35,47] Isoacteoside (12) H Rha H Cf OH OH H Cd, Ct, Csa [30,32,40,47] Isosyringalide-3 -rhamnopyranoside (13) H Rha Cm H OH OH H Ct [41] Osmanthuside B (14) H Rha Cm H H OH H Cd [29] Salidroside (15) H H H H H OH H Ct, Cd [32,38,42,43,44] Syringalide A-3 -rhamnopyranoside (16) H Rha Cf H H OH H Cd, Ct, Ct [32,40,41] Tubuloside A (17) Ac Rha Cf Glc OH OH H Cd, Cp, Ct [30,32,40] Tubuloside B (18) Ac Rha H Cf OH OH H Cd, Ct, Csa [30,31,47] Tubuloside C (19) Ac TA-Rha Cf Glc OH OH H Ct [30] Tubuloside D (20) Ac TA-Rha Cm Glc OH OH H Ct [30] Tubuloside E (21) Ac TA-Rha Cm H OH OH H Cp, Ct [41] Cistantubuloside A (22) H Rha Cf Glc H OH H Ct [11] Cistantubuloside B1/B2 (23) H Rha Cm/c-Cm Glc OH OH H Ct [11] Cistansinenside A (24) Ac Rha Cf H OH OMe H Csi [45] Jionoside D (25) H Rha Cf H OH OMe H Csi [45] Poliumoside (26) H Rha Cf Rha OH OH H Csi [45] Kankanoside F (27) H Rha H Glc OH OH H Ct [43] Kankanoside G (28) H Rha H Cf H OH H Ct [43] Eutigoside A (29) H H H Cm H OH H Csa [46] Cistantubuloside C1/C2 (30) H Rha Cf Glc OH OH OH (S/R) Ct [11] Salsaside D (31) Ac Rha Cf H H OH H Csa [47] Salsaside E (32) Ac Rha Cf H OMe OH H Csa [47] Salsaside F (33) Ac Rha H Cm OH OH H Csa [47] Crenatoside (34) Ct [34] ^aCf: trans-caffeoyl; Cm: trans-coumaroyl; c-Cm: cis-coumaroyl; Glc: -glucopyranose. Rha: -rhamnopyranose; TA-Rha: 2 -triacetyl-˛-l-rhamnopyranose; Ac:

acetyl. ^b Cd: C. deserticola; Ct: C. tubulosa; Cp: C. phelypaea; Csa: C. salsa; Csi: C. sinensis.
anti-radiation, etc. [15–17,40,48–50]. Among them, neuroprotection is becoming a hot topic. Some single components or fractions of PhGs have been reported to inhibit the apoptosis of neuronal cells induced by various chemicals [51–57], and their neuroprotections in vitro have also been proved by several animal models in vivo [58–64]. These results indicate that PhGs could be an attractive candidate for the treatment of neurodegenerative disorders, such as dementia or Parkinson’s disease.