Potential growth inhibition of freshwater algae by herbaceous plant extracts

Abstract

Algae often reduce aesthetic values and usability of freshwater as they can grow excessively and present in high biomass concentration. A biological approach to control algae growth by using plant-derived substances has received significant attention due to its minimal undesirable effects. To date, numerous herbaceous plants species are known to have antimicrobial properties. Nevertheless, their inhibitory potential against freshwater algae remains widely unexplored. This study attempted to explore algae inhibition potential using extracts from five herbaceous plants including Melastoma malabathricum, Cosmos caudatus, Pistia stratiotes, Etlingera elatior, and Cinnamomum cassia. Potential inhibitory effect of each plant extract on algae growth was determined through the percentage of algae growth reduction as compared to the control. Our results revealed that all, except Cinnamomum cassia, gave positive inhibitory effects on algae growth. The highest algae growth inhibition was observed in the treatment with Melastoma malabathricum extract, which inhibited up to 50% algae growth as compared to the untreated control. Meanwhile, treatments with Pistia stratiotes, Cosmos caudatus, and Etlingera elatior showed up to 42.6%, 35.3%, and 22.5% inhibition, respectively. Higher algae inhibition effects by Melastoma malabathricum and Pistia stratiotes extracts could be due to their flavonoids and alkaloids content. As an implication, this study suggests the potential use of widely available local plants such as Melastoma malabathricum and Pistia stratiotes to inhibit algae growth in freshwater ecosystems.