Antifouling and antipredatory activity of natural products of the seaweeds Dictyota dichotoma and Chaetomorpha linoides.

The seaweeds Dictyota dichotoma and Chaetomorpha linoides from the southeast coast of India were screened for anti-microfouling activity against biofilm bacteria, anti-macrofouling activity against brown mussels and feeding deterrence activity against the sea angel Monodactylus kottelati. The surface associated epiphytic bacteria were also isolated from seaweeds and screened for activity against biofilm bacteria. The acetone extracts showed a wide spectrum activity against biofilm bacteria and the algal metabolite was surface concentrated and non-polar in nature. The seaweeds also inhibited byssus production and attachment in brown mussels, and deterred feeding in the sea angel. The lower epiphytic bacterial number on the seaweed's surface compared to the surrounding seawater medium indicated selective inhibition or surface mediation. The epiphytic bacteria, which showed activity against biofilm bacteria, might also possibly play a role in seaweed defence strategies. The 50% deterrence of feeding activity at lower concentrations was not proportionate to the 100% inhibition concentration, which could be attributed to the adaptability of the fishes, an indication that the active substances are inhibitory in nature. This was further substantiated with the 100% recovery of mussels in a toxicity assay and the lower EC(50) values than LC(50) values in the mussel bioassay. The study indicates that the metabolites of both seaweeds have ecological significance and could possibly play a multifunctional role.

Anticancer activity of the ascidian polyclinum indicum against cervical cancer cells (HeLa) mediated through apoptosis induction.

The cytotoxicity-based chemotherapy treatment for cancer has significant side effects. Therefore, anticancer research is concentrated on identifying an effective drug with minimal side effects. The methanol extract of ascidian Polyclinum indicum and its column fraction PI-8 showed cytotoxicity against cervical cancer cells (HeLa) with an IC50 of 77.5 µg/mL and 1.12 µg/mL. Hoechst staining with PI-8 treated cells portrayed the apoptotic events in drug-induced apoptosis. The PI-8 markedly arrested G2/M and S phases in cell cycle. The occurrence of a second population of apoptotic cells in the range of lower Forward Scatter (FSC) and higher Side Scatter (SSC) compared to control cells indicated the characteristic feature of the cells dying of apoptosis. DNA fragmentation has established the apoptotic event. The study emphasized the fraction PI-8 of P. indicum as a potential lead compound for apoptosis targeted anticancer drugs. The molecular mechanism and chemotherapeutic potential of the fraction PI-8 needs further investigation.