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The major alkaloids present in very young leaves of Mitragyna speciosa from Malaysia were shown to be highly conjugated indoles, mitragynaline and corynantheidaline. Related compounds are also present in smaller amounts and two others were isolated and characterized (named mitragynalinic acid and corynantheidalinic acid). Mitragynaline is also present as a minor component in mature leaves of the plant.

Three new indole alkaloids with methyl chanofruticosinates skeletal system, viz., methyl 12-methoxy-N1-decarbomethoxychanofruticosinate, methyl 12-methoxychanofruticosinate and methyl 11,12-dimethoxychanofruticosinate, in addition to methyl 11, 12-methylenedioxy-N1-decarbomethoxychanofruticosinate, have been isolated from the leaves of Kopsia flavida Blume. The structures of these three new indole alkaloids were assigned by NMR spectral data using various 2D-techniques.

An investigation of the fresh leaves of Mitragyna speciosa has resulted in the isolation of a new alkaloid in addition to the indole alkaloids previously reported. The new alkaloid is the 3-dehydro derivative of mitragynine and its structure was elucidated by spectral means and chemical transformations. (-)-Epicatechin was also isolated from the leaves.