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Temporal changes in the production of secondary metabolites by marine organisms are fully
understood. Of all marine organisms, marine sponges are ranked at the top of the hierarchy
due to their ability to produce structurally novel natural secondary metabolites with bioactive
properties. However, variations in the abundance of bioactive compounds produced by
sponges may respond to physical constraints while the habitat spongesise, competition for
space, or against fouling may also cause changes in sponge secondary chemistry. Many of
these biotic or abiotic factors vary between months, seasons, and years resulting strong
temporal patterns in secondary metabolites. The present study thus investigated temporal
changes mediated by the crude extract of a Sri Lankan marine sponge species, Haliclona
(Soestella) sp, on in vitro phagocytic activity of Wistar rat peritoneal macrophages (PM).
Sponge samples were harvested from Unawatuna, Galle, Sri Lanka by scuba diving in 2013
and 2015, extracted with methanol/dichloromethane, followed by filtration through Whatman
No 1 filter papers and rotary evaporation. The resultant crude extract of Haliclona (Soestella)
sp (HSCE) was dissolved in 5% ethanol and tested for phagocytic capacity on Wistar
ratPMs at 2000, 1000, 500, 100, 10 µg/ml concentrations by ex vivo Nitro Blue Tetrazolium
assay (NBT).Absorbance was obtained as a measure of NBT dye reduction by PM cells and
the phagocytic capacity of these cells was calculated. The previous results, the phagocytic
activity of rat PMs evaluated ex vivo was significantly higher at HSCE doses of 10, 100 and
500 µg/ml (>1; P<0.01) than at 1,000 & 2,000 µg/ml doses (<1; P<0.05), indicative of
higher stimulation of PM cells by lower doses of the HSCE extracted from sponges collected
in 2013. However, a dose dependent increase in phagocytic activity by PM cells was
observed by HSCE extracted from sponge samples collected in 2015 (P<0.05), indicative of
the higher stimulation of PM cells by higher doses of the HSCE extracted from sponges
collected in 2015. Therefore, it is evident that a temporal change had occurred in the
secondary metabolites responsible for phagocytic activity produced by Haliclona (Soestella)
sp within a periods of two years (from 2013 -2015).
