Chromatographic estimation of asarones in Indian Acorus calamus Linn oil (tetraploid variety)
The roots of Acorus calamus Linn., growing in the plains of India, have been used for the treatment of various ailments 1,2 from very ancient times. Pharmacological studies have shown that the essential oil and asarone (trans and cis) possess relaxant, spasmolytic 3,4, and hypotensive 5 properties and have powerful insecticidal activity 6. The above properties have been shown to be due to the presence of asarones (trans and cis forms) which are present to the extent of 82% 7 in the essential oil of the Indian Acorus calamus Linn. (tetraploid variety). It has been shown that asarones (asarone and ?-asarone) are the important constituents of the oil which determine its quality. At present there is no method available for the estimation of asarones in the oil. It was, therefore, considered worthwile to develop a method for the quantitative estimation of the asarone content of the Indian calamus oil, which is obtained from the roots of Acorus calamus (tetraploid variety with chromosome number 2n = 36 (x = 9)).
Investigation of the oil showed that the hydrocarbon part could be separated easily by adsorbing it on a column of alumina and then eluting it with petroleum ether; the asarone part could then be eluted from the column with a mixture of benzene and ether (9:1). On the basis of the above observation the following method was, therefore, developed.
Method
1 g of the oil of A. calamus (tetraploid variety) was chromatographed over 50 g of grade I (Brockmann) alumina packed in a column of 2 cm diameter. It may be observed from the elution curve (Fig I - not included) that 35 mL of petroleum ether (bp 40-60°C) elutes all the hydrocarbons and the 65 mL of mixtures of benzene and ether (9:1) elutes all the asarone present in the oil. The solvent is removed, the last traces being removed under vacuum and the residue weighed. The percentage of asarones can be calculated as follows:
%Asarones = 100 * (wt of asarones) / (wt of oil)
The method could not be verified by comparison with some conventional method. Nevertheless, we examined different samples of the oil distilled at various stages and found that the results were found to agree within 1%. The oils distilled in 1963 and 1964 gave 80.7% and 79.9%, respectively, as the asarone content.
The authors are grateful to Dr I C Chopra, Director of this laboratory, for his keen interest in the above investigation.
References
1. KM Nadkarni. The Indian Materia Medica. Bombay, 1927, p 26
2. IC Chopra e.a. Indian J Med Res 42 (1954) 381
3. PK Dass e.a. Arch Intern Pharmacodyn 135 (1962) 167
4. PC Dandiya e.a. Brit J Pharmacol 20 (1963) 436
5. JD Sharma e.a. Indian J Med Res 50 (1962) 61
6. Annual Report, Regional Research Laboratory, Jammu, 1963-1964, p 19
7. E Guenther, The Essential Oils, Vol VI, D Van Nostrand Co, Inc, NY 1952, p 115
Article: MM Chopra e.a. Journal of Chromatography 17 (1965) 195-196
