PHYCOCHEMICAL STUDIES ON FRESH-WATER GREEN ALGAE OF KARACHI

Useful implication of fresh-water algae and algal products had been the main source of motivation for present systematic investigations in their ecological, biochemical and nutritional aspects as the climatic conditions are conducive to the growth of algae in abundance in Pakistan. The present study relates to exploring the possibility of the same. Experiments were carried out to study the phycochemical constituents of green algae present in fresh-water environment of Karachi and its suburb. Cladophora glomerata (L) Kutzing, Spirogyra dictyospora jao and Entermorpha procera Ahlner were selected for the present studies due to their presence in abundance in pure form. These algae were collected from Hub valley and Kalri Lake. Entromorpha procera Ahlner from Hub valley region is the first report of any member of Ulvales from fresh-water environment in Pakistan. The research work has been carried out in two parts. Part-I deals with the analysis of green algae for their biochemical constituents of nutritional and manorial importance. This includes the determination of moisture, ash, inorganic elements, soluble carbohydrates, total nitrogen, crude protein and fat contentPresent studies clearly indicated that 1) fresh-water green alga Spirogyra dictyspora is a better species as compared to other fresh-water green algal species used in the study, 2) in general the algae collected from Hub valley are relatively better in nutrient content than species present in Kalri Lake, 3) the species from Hub valley are even richer in nutrients than many seaweeds used world wide as food, fodder and fertilizer having high values of total nitrogen, crude protein, fat and phosphorus content. Although these algae have been found toxic, yet it may be necessary to evaluate their food value by feeding experiments before being introduced for human consumptionPart-II deals with the isolation and identification of saturated and unsaturated fatty acids, hydrocarbons, sterols and steroids from these fresh-water algae by implying modern sophisticated techniquesC16:0 (palmitic acid) was found to be most common and predominant fatty acid among the saturated fatty acids in these algae. Various medium and long chain mono and polyunsaturated fatty acids were present (C14: 1-C18:3) in the algae used in present studyFree saturated and unsaturated fatty acids are distributed in a narrow molecular weight range (C9-C18) and do not show any significant qualitative variation between the algal species Cladophora glomerata, Spirogyra dictyospora and Enteromorpha procera harvested from Hub valley area of Karachi. However, the molecular weight range of free and liberated fatty acids of cladophora glomerata collected from Kalri Lake of Karachi is C14-C25Significant number of paraffings and olefins of low to high molecular weight were identified in Spirogyra dictyospora (C14-C25) and in cladophora glomerata (C15-C33) of Hub valley area. No hydrocarbon was identified in Enteromorpha procera of the same locationβ-sitosterol, cholesterol, cholestanol and ∆8, 14,22(28)-stigmastarrienol were present in cladophora glomerata species of Kalri Lake. β-sitosterol was also isolated from Spirogyra dictyospora but not detected in Cladophora glomerata and Entermorpha procera species of Hub valley areaOne steroidal galactoside was also isolated from Spirogyra dictyospora in substantial amountA cycloartanol like compound having pentacyclic triterpene skeleton of empirical formula C30H50O was found in Cladophora glomerata collected from Hub valley areaAmong the algae studied, Spirogyra dictyospora seems to be capable of synthesizing diverse type of chemical compoundsPresent phycochemical studies on fresh-water green algae of Karachi and its suburb have indicated the enrichment of spirogyra dictyospora of Hub valley over the other species studied, in possessing many important nutrients and chemical compounds in appreciable magnitude and reportedly of considerable importance in the assessment of manorial, nutritional and medicinal value of algae