The dried rhizomes of genus Atractylodes (family: Asteraceae) plants, which have been classified into “Baekchul” and “Changchul”, have been used to treat wind-phlegm-caused headache, diarrhea, and phlegm-induced digestive disorders1). In the Korean pharmacopeia, four species of Atractylodes rhizomes are used as Changchul or Baekchul: the rhizomes of A. lancea DC. (AL) and A. chinensis Koidz. (AC) are registered as Changchul; and those of A. macrocephala Koidz. (AM) and A. japonica Koidz.(AJ) are registered as Baekchul2).
Atractylodes rhizomes contain diverse chemical compounds such as polyacetylenes, sesquiterpenes, and essential oils, and those compounds are thought to exert the pharmacological effect of the rhizomes3–5). Of those compounds, polyacetylenes and sesquiterpenes most occurred in Atractylodes rhizomes; however, the occurrences of compounds and the presentation of chemical structures were insufficiently arranged by each Atractylodes species6).
Polyacetylene (or polyethyne by the IUPAC name) consists of polymerization of acetylene, a alkyne-type hydrocarbon, with a chain of olefin groups repeated, and possesses long carbon chains with alternating single and double bonds of either cis or trans geometry7). Hydrogen atoms can be attached at conjugated carbon atoms and they can also be replaced by a functional group8).
Therefore, in this study, the chemical structures of polyacetylenes were classified by their chemical backbones and the species of genus Atractylodes where the compounds were contained was presented. Additionally, phytochemical characteristics of those compounds were also discussed through extraction or processing. Thereafter, their pharmacological activities could be understood.
Ⅱ. Materials and methods
1. Paper search
The literatures from 1970 to January 2016 were searched using a variety of electronic bibliographic databases: Korean databases, including the Korea Education and Research Information Service, National Discovery for Science Leaders, the Korean Studies Information Service System, and Korea Institute of Science and Technology Information, Korean Traditional Knowledge Portal, Oriental Medicine Advanced Searching Integrated System, KoreaMed, eArticle, and DBpia; Chinese databases including the China National Knowledge Infrastructure; Japanese databases including Citation Information from the National Institute of Informatics and Japan Science and Technology Information Aggregator, Electronic; and electronic global databases including PubMed, Web of Science, ScienceDirect, and Google Scholar.
2. Search terms and inclusion criteria
The search terms used in the present study were “창출”, “백출”, “蒼朮”, “白朮”, “苍术”, “白术”, “Changchul”, “Baekchul”, “Changzhu”, “Baizhu”, “Sojutsu”, “Byakujutsu”, “Atractylodes rhizome”, “Atractylodes macrocephala”, “Atractylodes japonica”, “Atractylodes lancea”, “Atractylodes chinensis”, “Atractylodes ovata”, and “Atractylodes koreana”
Studies in accordance with the following criteria were included: 1) original articles (not review articles; 2) medicinal part is the rhizome of Atractylodes plant; 3) polyacetylenes were isolated or analyzed using analytical tools from Atractylodes rhizomes; 4) chemical names including International Union of Pure and Applied Chemistry (IUPAC) names or chemical structures of polyacetylenes were presented; and 5) no language limitation.
Chemical structures were manually drawn using ChemDraw software (v. Ultra 10.0; Cambridge Soft, Cambridge, MA, USA). If necessary, author amended incorrect chemical structures or names in the studies.
Ⅲ. Results and discussion
1. Diene–diyne types of Atractylodes polyacetylenes
Polyacetylenes of diene-diyne types were classified into furan-ring-attached, alcohol-attached, acetyl-attached, and two more functional groups-attached compounds. Seven atractylodin-related acetylenes, which contained a furan-ring at the terminal carbon, consisted of nine carbons. Another seven polyacetylenes comprised 14 carbons with double bonds at C-6 and C-12, and triple bonds at C-8 and C-10. Diacetyl atractylodiol was acetylene with thirteen carbons and (2E,8E)-decadiene-4,6-diyne-1,10-diol-1-O-β-D-glucopyranoside was the only polyacetylene which consisted of 10 carbons and glucopyranose. Of those compounds, atractylodin was most reported in previous reports and was contained in AL, AC, AJ, and AK (A. koreana). However, no diene-diyne types were reported to be contained in AM (Table 1).
Table 1AL, A. lancea; AC, A. chinensis; AM, A. macrocephala; AJ, A. japonica; AK, A. koreana.
2. Triene–diyne types of Atractylodes polyacetylenes
As shown in Table 2, 21 compounds of triene–diyne type polyacetylenes possessed 14 carbons with double bonds at C-2, C-8, and C-12, and triple bonds at C-4 and C-6. Functional groups of these compounds were isovaleryloxy, senecioyloxy, methylbutyryl, methylpropionyl, and acetoxy, most of which were positioned at C-12 or C-14. Another 14 carbon polyacetylenes showed different positions of double and triple bonds: double bonds at C-4, C-6, and C-12, and triple bonds at C-8 and C-10, also with the functional groups such as acetoxy, isovaleryloxy, senecioyloxy, or methylbutyryloxy attachments. Of the nine polyacetylenes with 13 carbons, eight polyacetylenes contained two triple bonds at C-7 and C-9, but double bonds were at different locations: three double bonds at C-1, C-5, and C-11, while at C-3, C-5, and C-11, which were attached by di-acetate, except for one compound with a ferulate. There were three double bonds at C-2, C-4, and C-10, and two triple bonds at C-6 and C-8 with the acetate group attached remaining. Most compounds originated from AM, followed by AL and AO (A. ovata), and those from AC or AJ were much less common.
Table 2AL, A. lancea; AC, A. chinensis; AM, A. macrocephala; AJ, A. japonica; AO, A. ovata.
3. Monoene–diyne types of Atractylodes polyacetylenes
Four monoene-diyne type polyacetylenes were reported to be a single double bond and two triple bonds, consisting of nine, ten, twelve, and thirteen carbons, with furan ring or sugars attached (Table 3).
AL, A. lancea; AM, A. macrocephala; AO, A. ovata.
4. Influence of processing on physicochemical and biological properties of Atractylodes polyacetylenes
1) Physicochemical properties
Polyacetylenes experience diverse chemical changes in the process of extraction, especially during boiling with water. Atractylodin (C18H10O), which is the most reported polyacetylene from the essential oil in Atractylodes rhizomes, is an alkyne-polyacetylene containing a 2-nonyltetrahydrofuran skeleton and it has properties such as instability in the air and light due to an unsaturation structure, which leads it to produce brown insoluble resin rapidly in air at room temperature83). Atractylodin is highly unstable and becomes brown colored when in contact with air, which makes an oil cavity in primitive oil ducts or lysigenous secretory tissues where atractylodin as well as other polyacetylenes are accumulated. This leads to a brown color on a cut surface of the rhizome25). When oxidized at a high temperature (120℃), atractylodin turns to the cis-form of atractylodinol, i.e. a H attached to a terminal methyl carbon substituted with OH . Atractyloyne and (4E,6E,12E)-3-isovaleryloxy-tetradeca-4,6,12-triene-8,10-diyne-1,14-diol were converted to (4E,6E,12E)-tetradeca-4,6,12-triene-8,10-diyne-1,3,14-triol, and 14--methylbutyryltetradeca-2E,8E,10E-trien-4,6-diyn-1-ol was deacylated when the rhizomes were extracted by boiling in water62).
2) Biological properties
Processing of Atractylodes rhizomes also influenced the physicochemical properties and absorption of polyacetylenes. The extraction efficiencies of atractylodin and (4E,6E,12E)-tetradecatriene-8,10-diyne-1,3-diyl diacetate from Atractylodes rhizomes were decreased when the rhizomes were stir-fried with bran compared to crude rhizomes84–86). However, processing by stir-frying with bran affected these in vivo in different ways. The plasma concentration of atractylodin was increased after Atractylodes rhizomes were processed by stir-frying with bran rather than crude rhizomes, which indicated that processing of Atractylodes rhizomes can increase the absorption of atractylodin87). Stir-frying of Atractylodes rhizomes with wheat bran could promote and accelerate the absorption of (4E,6E,12E)-tetradecatrinen-8,10-diyne-1,3-diyl diacetate and its concentration was highest in the spleen, possibly increasing the spleen-tonifying effect according to the traditional theory74).
5. Chemical stabilities of Atractylodes polyacetylenes
Stability is another concerning issue as the occurrences of bioactive polyacetylenes can be changed under certain circumstances, like drying of the rhizomes under the sun. Atractylodin, atractylodinol, and acetylatractylodinol were reported to have 1-cis isomers, (1Z)-atractylodin, (1Z)-atractylodinol, and (1Z)-acetylatractylodinol. The proportions of those 1-cis isomers were less than 1-tran isomers as the 1-cis isomers could be formed during drying process of the Atractylodis rhizomes under the sun: i.e. (1E)-acetylatractylodinol is rapidly isomerized to (1Z)-acetylatractylodinol49). On the one hand, the stabilities of 1-cis isomers were weaker than those of 1-trans isomers: (1Z)-acetylatractylodinol more expeditiously disappeared in n-hexane solution compared to (1E)-acetylatractylodinol dissolved in same solvent in the freezer. On the other hand, 1-cis isomer of atractylodin was relatively increased up to a similar ratio with its parent compound, atractylodin, in freezer storage, indicating that atractylodin was considerably instable than its isomer and different from those two polyacetylenes, (1E)-atractylodinol and (1Z)-atractylodinol, which showed the same degree of instability49).
6. Pharmacological activities of Atractylodes polyacetylenes
In terms of pharmacological activity, polyacetylenes exhibited structure-activity relationships: the introduction of an acyl group into a compound increased the inhibitory effect against NO production; i.e., 14-acetoxy-12-senecioyloxytetradeca-2E,8E,10E-trien-4,6-diyn-1-ol, 14-acetoxy-12-β-methylbutyryltetra-deca-2E,8E,10E-trien-4,6-diyn-1-ol, and 14-acetoxy-12-β-methylbutyryltetradeca-2E,8E,10E-trien-4,6-diyn-1-ol showed lower IC50 level than 12-senecioyloxytetradeca-2E,8E,10E-trien-4,6-diyn-1-ol, 14-β-methylbutyryltetradeca-2E,8E,10E-trien-4,6-diyn-1-ol, and 14-β-methylbutyryltetradeca-2E,8E,10E-trien-4,6-diyn-1-ol64). Moreover, the compounds with negative specific rotation, 14-acetoxy-12-senecioyloxytetradeca-2E,8E,10E-trien-4,6-diyn-1-ol and 14-acetoxy-12-β-methylbutyryltetradeca-2E,8E,10E-trien-4,6-diyn-1-ol, showed stronger inhibitory effects against NO production than those with positive rotation, 14-acetoxy-12-senecioyloxytetradeca-2E,8Z,10E-trien-4,6-diyn-1-ol and 14-acetoxy-12--methylbutyryltetradeca-2E,8Z,10E-trien-4,6-diyn-1-ol63). Deacylated product of 14-β-methylbutyryltetradeca-2E,8E,10E-trien-4,6-diyn-1-ol, due to boiling extraction with water, results in diminished anti-inflammatory activity63).
Other studies also provide us with pharmacologically explainable clues that could be employed to interpret the traditional therapeutic properties of the Atractylodes rhizomes. Atractylodiol and diacetyl-atractylodiol from A. japonica can stimulate the contractility of the distal colon in rats by inhibiting the mechanism of nitrergic–purinergic relaxation52). Atractylodin, atractylodinol, acetylatractylodinol, and 4,6,12-tetradecatriene-8,10-diyne-1,3,14-triol from A. lancea can promote delayed gastric emptying17). These acetylenes, even though the traditional therapeutic properties cannot be entirely explained, are considered key elements for pharmacological accounts of the effects of Atractylodes rhizomes that have been used to treat gastrointestinal disorders.
Through bibliographical research, polyacetylenes from the Atractylodes rhizomes were divided into three categories; diene–diyne types, triene–diyne types, and monoene–diyne types. Those compounds showed a variety of moieties according to diverse functional groups, with following characteristics:
The present study will help to understand the physicochemical and pharmacological properties of polyacetylene from Atractylodes rhizomes.