H. pluvialis is the potential source of natural astaxanthin, which is considered as super antioxidant. In the present investigation, astaxanthin was extracted from the encysted cells of H. pluvialis with acetone, methanol, DMSO and hexane, the crude extracts were tested for four strain (Escherichia coli, Salmonella typhi, Vibrio cholera and Staphylococcus aureus)of bacteria for the antibacterial activity. Highest antibacterial activity was observed as 10.2 ±0.20 mm extracted with acetone on Escherichia coli while as least antibacterial activity was found as6.1±0.0 mm extracted with hexane on Vibrio cholera. Keywords: Haematoccoccus pluvialis; Astaxanthin; Antibacterial.

In the present investigation, effect of biomass, crude astaxanthin of Haematococcus pluvialis on the different hepatic and antioxidant enzymes against toxin, carbon tetrachloride (CCl4) induced toxicity on male Albino Wistar rat, weighing 200-220g which were compared with the commercially available astaxanthin and ascorbic acid all are mixed in liquid paraffin and feeding (orally) of 100µg/kg b.w of commercially available astaxanthin, biomass, crude extract, and ascorbic acid was started 2 weeks before to CCl4 treatment. The animals were sacrificed after 24 h of CCl4 treatment, collected samples, for the evaluation of hepatic and antioxidant enzymes Biomass (100µg/kg b.w) treated groups restored maximum damage induced by the CCl4, when results were compared with the toxin treated group. These results indicate that H. pluvialis biomass and crude extract showed umpteen hepatoprotective and antioxidant activity and thus can be used for various food formulations for human welfare.

The aim of the present study was to investigate the impact of light and dark (L/D) period on biosynthesis of astaxanthin in green alga Haematococcus pluvialis. The astaxanthin was extracted from H. pluvialis with dimethyl sulfoxide, and the astaxanthin content was determined by the ultraviolet spectrophotometer. H. pluvialis was incubated under 10:14 h (L/D) period exposed to sunlight at 32 ± 2°C temperature, the astaxanthin biosynthesis was compared with the culture which was incubated in controlled air-conditioned culture room of 16:8 h (L/D) period at 25 ± 2°C. Highest astaxanthin content was found as 0.045 µg/mL in H. pluvialis culture which was exposed to sunlight under 10:14 h (L/D) on the 9 th day of study. Under 16:8 h (L/D) period at 25 ± 2°C, the highest astaxanthin content was found as 0.04 µg/mL on the 17 th day of study. From our present investigation, it is apparent that the 10:14 h (L/D) period is more effective in promoting astaxanthin content of green alga H. pluvialis.

Haematococcus pluvialis is one of the richest sources of natural astaxanthin which is considered as "super anti-oxidant." Astaxanthin has umpteen applications in the nutraceuticals, cosmetics, food, and aquaculture industries, can significantly decimate free radicals, oxidative stress and help human body maintain a healthy state. With extraordinary potency and increase in demand, astaxanthin is one of the high-value microalgae products of the future. This comprehensive review summarizes different sources of astaxanthin, occurrence, life cycle of H. pluvialis and applications of astaxanthin for human and animals.