Quality Assessment of selected liriodenine bearing plants endemic to Thailand

Abstract

Liriodenine, an aporphine isoquinoline alkaloid, has many biological activities, including anti-platelet, anti-fungal and anti-microbial actions. Additionally previous studies revealed that it had potent cytotoxicity against a number of cancer cell lines. This study aimed to determine liriodenine content in selected Thai medicinal plants by TLC image analysis compared to HPLC. Twenty-eight plant materials in Magnoliaceae, Annonaceae and Nelumbonaceae were collected from natural sources in Thailand. Crude extracts were prepared by Soxhlet extraction with 95% ethanol. Validations of both methods were performed including linearity, accuracy, precision and sensitivity based on International Conference of Harmonization (ICH) guideline. Top three highest contents of liriodenine were found in Michelia longifolia (bark), Michelia champaca (bark) and Nelumbo nucifera (leaf) which are also used as crude drug in various Thai traditional recipes. Fifteen different locations throughout Thailand of each medicinal plant were then examined for pharmacognostic specification to establish their standardization for quality assessment. Pharmacognostic parameters from Michelia longifolia bark revealed that the acid-insoluble ash, total ash, loss on drying and water content should be not more than 3.49, 5.74, 7.17 and 6.67 % of dry weight respectively; while ethanol and water-soluble extractive should be not less than 3.85 and 8.25 % of dry weight respectively. Michelia champaca bark showed that the acid-insoluble ash, total ash, loss on drying and water content should be not more than 2.98, 6.25, 5.62 and 7.37 % of dry weight respectively; while ethanol and water-soluble extractive should be not less than 6.71 and 12.38 % of dry weight respectively. Pharmacognostic parameters of Nelumbo nucifera leaves revealed that the acid-insoluble ash, total ash, loss on drying and water content should be not more than 2.61, 9.62, 7.69 and 7.06 % of dry weight respectively; while ethanol and water-soluble extractive should be not less than 6.24 and 9.51 % of dry weight respectively. In summary, calibration showed good linear correlation coefficients (R2 > 0.995) over the range of concentration 5-200 µg/mL. Method validation of both methods was successfully developed performing reliability and sensitivity. TLC image showed a well-defined fluorescent spot of liriodenine at the Rf value of 0.75 under UV 365 nm, while HPLC chromatogram indicating liriodenine peak at 11 min of retention time. Both proposed methods could be used as a tool for the quantification of liriodenine in medicinal plants. There was no significant difference between the results of both analytical methods (p>0.05). TLC image could be applied for analysis of the content of this compound because it is simple, rapid and inexpensive. Moreover, the fluorescent coloring spot which was a dominant characteristic of liriodenine on TLC plate allowed TLC image analysis to be more suitable and convenient for further development.