Water based plant extracts are widely used for various medicinal applications. Due to its simple and economical extraction
process, herbal based industries prefer water based extraction. The water based extracts are prone to microbial growth due to
presence of moisture as they are hygroscopic in nature. Microbial growth in herbal extracts can be controlled using suitable
excipients. This study investigates and compares microbial contamination tendency in formulated and unformulated herbal
preparations with respect to their moisture content. Water based leaf extract powder of Orthosiphon Stamineus (Benth) was
selected. Moisture content and microbial limit tests were performed immediately for the fresh extract powder and in its final
formulation. Both the extract and formulation were stored at room temperature for three months exposed and unexposed to air.
Microbial population and weight changes were monitored on a dynamic moisture balance over a period of 3 months. The study
revealed that the unexposed formulation still contained moisture however had less moisture content and microbial growth. The
findings provide an insight into a possible approach for formulating moisture-sensitive pharmaceutical products, especially dry
powder preparations for use in tropical countries with high humidity environment.