Studies On Chemical Constituents From Coleus Forskohlii And Quality Evaluation Of Its Extract

Coleus forskohlii(Willd) Briq.(Labiatae),which mainly distributes in Indian and Yunnan Province of China,is a folk medicine against asthma,cough,bronchitis, etc.However,the content of active ingredients in the products made from domestic plants is extremely low.So it's necessary to study and develop the domestic species further.In our previous research work,an extract of C. forskohlii(CFE) was prepared by macroporous resin column chromatography. The pharmacological studies showed that CFE had the significant inhibitory effect against the contraction of guinea pig's trachea induced by histamine in vitro. Therefore,on the basis of the previous results,the present study focuses on the chemical constituents of C.forskohlii and the quality evaluation of CFE.The chemical constituents of C.forskohlii were studied.Eighteen compounds were isolated by various column chromatographic methods,and their structures were identified as forskolin G(1),forskolin J(2),1,6-diacetyl-9-deoxy-forskolin (3),forskolin A(4),forskolin H(5),6-acetyl-1-deoxyforskolin(6), forskolin D(7),1,9-dideoxy-7-deacetylforskolin(8),isoforskolin(9),forskolin I (10),chamaecydin(11),6α-hydroxydemethylcryptojaponol(12),α-cedrene(13), oleanolic acid(14),betulinic acid(15),stigmasterol(16),β-sitosterol(17),stearic acid(18).Compounds 11～13 were obtained from the genus Coleus for the first time,and compound 14 was obtained from C.forskohlii for the first time.An HPLC-ELSD method was developed and validated for the determination of isoforskolin and forskolin in CFE and the commercial extracts of C.forskohlii. The HPLC separation was carried out on a Kromasil C₁₈(4.6 mm×250 mm,5μm) column,using methanol-water(63:37) as mobile phase.The flow rate was 1 ml/min,the temperature of column was 40℃,and the drift tube temperature of ELSD was 90℃.Linearity was confirmed for isoforskolin and forskolin.The average recoveries(n=6) of isoforskolin and forskolin were 97.88%(RSD 3.33%), 103.15%(RSD 4.98%),respectively.The contents of 7 batches of samples showed that the content of forskolin was higher than that of isoforskolin in the extracts prepared by C.forskohlii from abroad,forskolin was not detected in the extract prepared by C.forskohlii from China,and the content of isoforkolin in CFE was significant higher than that in commercial extract from domestic plants.In the end,a review on the research progress of C.forskohlii is presented.