Curcapitoside, a novel glucosyl-fused phenanthropyran isolated from Curculigo capitulata

Total synthesis of sinenside A

The first total synthesis of norlignan glucoside sinenside A has been accomplished. An intramolecular acetalization reaction has been employed as the key skeletal construct to forge the central cyclic disaccharide core. The trans-1,2-diol configuration present in the cyclic disaccharide of this natural product is unique and has been addressed by setting this configuration at the beginning. A 1,2-orthoester group has been selected as a handle for both sp glycosidation and for differentiation of the C2'-OH (that participates in the key acetalization reaction) of the sugar unit.

Medicinal plants of genus Curculigo: traditional uses and a phytochemical and ethnopharmacological review

ETHNOPHARMACOLOGICAL RELEVANCE

In the genus Curculigo, Curculigo orchioides Gaertn, Curculigo capitulata (Lour) O. Ktze and Curculigo pilosa (Schumach. & Thonn.) Engl are often used in traditional medicine. Curculigo orchioides is used for the treatment of impotence, limb limpness, arthritis of the lumbar and knee joints, and watery diarrhea in traditional Chinese medicine, and also used as a potent immunomodulator and aphrodisiac in the Ayurvedic medical system. Curculigo capitulata is used for the treatment of consumptive cough, kidney asthenia, impotence and spermatorrhea, hemorrhoids, asthma, jaundice, diarrhea, colic and gonorrhea in traditional Chinese and India medicine, and to treat urinary tract infection, acute renal pelvis and nephritis, nephritis-edema, cystitis, nephrolithiasis, hypertension and rheumatic arthritis in traditional Dai medicine. Curculigo pilosa are applied to treat gastrointestinal and heart diseases in Africa.

AIM OF THE REVIEW

This review aims to exhibit up-to-date and comprehensive information about traditional uses, phytochemistry, pharmacology and toxicology of medicinal plants in the genus Curculigo, and has an insight into the opportunities for the future research and development of Curculigo plant.

METHODS

A bibliographic investigation was performed by analyzing the information available on Curculigo plant from worldwide accepted scientific databases (Pubmed, Scopus and Web of Science, SciFinder, Google Scholar, Yahoo). Furthermore, information also was obtained from some local and foreign books on ethnobotany and ethnomedicines.

RESULTS

Curculigo orchioides, Curculigo capitulata and Curculigo pilosa have been used as traditional medicine to treat kinds of diseases such as impotence, limb limpness, gastrointestinal and heart diseases, etc. Phytochemical investigation of eight species of the genus Curculigo has resulted in identification of more than 110 compounds. The content of curculigoside is used as an indicator to evaluate the quality of rhizome of Curculigo orchioides. The medicinal plants have showed a wide spectrum pharmacological activities, including adaptive, immunostimulatory, taste-modifying and sweet-tasting, antioxidant, mast cell stabilization, antihistaminic and antiasthmatic, hepatoprotective and neuroprotective activity. Toxicological test indicated that Curculigo orchioides at the dose of 120 g/kg after administrating rats for 180 days may cause injury of liver and kidney.

CONCLUSION

The medicinal plants of genus Curculigo have emerged as a good source of the traditional medicines. Some uses of these plants in the traditional medicines have been validated by pharmacological investigation. However, the mechanism of their actions should be further elucidated; the particular constituent responsible for toxicity should be isolated and identified, and the target tissue and mechanism of toxic ingredients also deserve to be further investigated; more reference substances should be prepared, and sophisticated analytical technologies should be developed to comprehensively assess the quality of Curculigo herbs. These investigations will be helpful for further utilization of the plants of genus Curculigo.

Novel norlignan glucosides from rhizomes of Curculigo sinensis

Eight norlignan glucosides, including two novel skeleton-rearranged compounds, sinenside A (1) and B (2), and six known compounds, crassifoside D (3), capituloside (4), a mixture of (1S,2R)-1-O-methylnyasicoside (5), (1R,2R)-1-O-methylisonyasicoside (6), and a mixture of (1S,2R)-1-O-methylcurculigine (7) and (1R,2R)-1-O-methylisocurculigine (8), were isolated from the rhizomes of Curculigo sinensis. Compounds 3-8 were isolated for the first time from this plant. Structures of the isolated compounds were established by spectroscopic analysis, including UV, IR, HRESI-MS, and 1D/2D NMR, and hydrolysis experiments. The free radical scavenging activity of the isolated compounds was evaluated by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. All the isolated compounds showed strong radical scavenging activities.

Three new norlignans from Curculigo capitulata

From the ethanolic extract of the rhizomes of Curculigo capitulata have been isolated, and structurally elucidated by spectral evidences and chemical methods, three new norlignans, capituloside (1), a mixture of curculigenin (2) and isocurculigenin (3), along with four known compounds (4-7), a mixture of 1-O-methylcurculigine (4) and 1-O-methylisocurculigine (5) and a mixture of curculigine (6) and isocurculigine (7).

Capitulatin B, a new eudesmane derivative from Curculigo capitulata, and revised assignment of 13C NMR data of 6alpha,15alpha-epoxy-1beta,4beta-dihydroxyeudesmane

A new eudesmane derivative named capitulatin B (1) along with 6alpha,15alpha-epoxy-1beta,4beta-dihydroxyeudesmane (2) has been isolated from the rhizomes of Curculigo capitulata. The structure of compound 1 was established as 4alpha,6alpha-epoxy-1beta-hydroxy-4beta-methyleudesmane, and the 13C NMR data of compound 2 was reassigned on the basis of the spectral data, including 1D and 2D NMR (HMQC, HMBC, COSY, ROESY).

New chlorine-containing phenoloid from Curculigo capitulata

A new chlorine-containing phenoloid, named capitulatin A, has been isolated from the rhizomes of Curculigo capitulata. Its structure was established as 2,4-dichloro-3-methyl-5-hydroxy-6-methoxylphenol-beta-D-xylopyranosyl (1 --> 6)-beta-D-glucopyranoside (1) on the basis of the spectral data and chemical evidence.