MSc

An experiment was conducted at the Department of Plantation Crops and Spices, College of Horticulture, Kerala Agricultural University, Vellanikkara, Thrissur during 2003-2005 to study the influence of stage of harvest, drying method and method of extraction and storage on phytochemistry and antimicrobial property of Coleus amboinicus Lour.

Stages of harvest did not alter the quality of the plant Coleus amboinicus to a considerable extent. All the quality parameters viz., total sugars, amino acids and crude extractables were maximum at fifth month after planting, but there was only proportionate increase. The plant also maintained the same sugar and amino acid profile through out the growth period. GC profile of the essential oil revealed that the percent concentration of individual components did not vary much, with one of the components maintaining dominance in its reserve at all stages of harvest. With these results, the study concludes that Coleus amboinicus could be harvested and used as a drug during its entire growth period.

Among different methods of drying, ambient temperature drying was more efficient than sun and oven drying as it recorded more sugars and amino acids. GC profile of essential oil from dried leaves showed that the concentration of all the components except component B was very low in all the methods of drying and all the components maintained the same per cent area in samples dried at ambient temperature. When fresh and dry samples were compared, the former was superior in all the quality parameters.

Among the various extracts made out of Coleus amboinicus leaves, alcohol extracts and its residues made from fresh leaves recorded highest sugar as well as amino acids contents. When the extracts were stored, the sugar content increased at a slow rate where as the amino acid content decreased at a faster rate.

In the studies on microbial growth in the extracts during storage lower microbial load was assessed in alcohol extracts and its residues in comparison to water extract and its residues.

Considering the above findings alcohol extracts and its residues seemed to be the best extracts for storing Coleus amboinicus for drug purpose.

GC profile of the stored essential oil revealed that the percent concentrations of components did not vary considerably during storage. This may be considered as positive indication for preserving the oil for future use.

Anti-microbial assay of Coleus amboinicus water extracts revealed that the extract inhibited the growth of human pathogens viz., Escherichia coli and Staphylococcus species and plant pathogens viz., Collectotrichum species and Fusariam species. Further field and clinical studies are required to confirm these findings.

To conclude, the plant Coleus amboinicus was effective as a drug throughout its active growth stage, in the fresh form. Fresh sample was ideal with respect to quality. Drying at ambient temperature was found to be the best method of drying. Alcohol extract was found best for the preparation of crude drug extract of C. amboinicus. Water extract of leaves inhibited the growth of select human and plant pathogens in vitro, however this needs confirmation through massive clinical and field studies.