Fourier transform infrared (FT-IR) spectroscopic investigations of four agarophytes from northern Arabian sea

The fresh specimens of Champia compressa Harvey, Gelidium usmanghanii Afaq-Husain and M. Shameel, Gracilaria foliifera (Forsskål) Børgesen and Hypnea musciformis (Wulfen) J. V. Lamouroux, were collected from the coastal areas of Karachi (Pakistan) and their yield of agar was observed. With preextraction technique the percentage of algal yield was found to range from 13 to 28%. High quality gel strength was determined by modulus of elasticity i.e. (550 – 612g/cm) and 1090 kPa and extraction time was 2 hrs. The structure of agar and agar contents were investigated by FT-IR spectroscopy for the first time from Pakistan. The results revealed some interesting characters (non sulphated -D galacto pyranose residues, 3,6 anhydro galactose vibration), which were not reported earlier. Introduction The coastline of Pakistan is about 885 km long and rich in algal vegetation found either in growing and in drift form or attached to the rocks, occurring also in the sandy and rocky bottom of the pools (Shameel and Tanaka 1992). Algae produced a number of biologically and chemically active compounds such as aldehydes, fatty acids, halogenated compounds, sterols and terpenes (Aliya and Shameel 2003, Shahnaz and Shameel 2008, 2009). According to Bhadury and Wright (2004) algal metabolites have antibacterial, antifungal, and antibiofouling properties. Additionally, natural products isolated from seaweeds have pharmaceutical and medicinal uses in various parts of the world (Smit 2004). Seaweeds the imperative revenue generating resources of the marine environment, have a fundamental and important position in traditional drug of all ancient civilizations of the world, i.e. Greek, Roman, Chinese and Indian and are exploited as vermifuges, aesthetics and antibiotics in the treatment of cough, wounds, gout, goiter, hypertension, cancer, venereal and a variety of other diseases (Smit 2004, South and Whittick 1987, Sridharan and Dhamotharan 2012). They also provide alginate, agar and carrageenan some of their carbohydrates (polysaccharides) are being used in the preparation of toothpastes, soaps, shampoos, and as a thickening agent in ice creams and milk (NAAS 2003). Particularly agar is widely used in leather, cosmetics, paper, textile, dairy and pharmaceutical industries. Moreover, it is the major component of culture media for microbiology laboratory (NAAS 2003). A number of research work have been reported on sulfated polysaccharides commonly known as agar and cell wall constituents of red algae (Akahane and Izumi 1976, Villanueva and Montaño 1999, Freile-Pelegrin and Murano 2005, Laurienzo 2010, Villanueva et al. 2009, 2010a, b). The agarose is the major component of agar, the repeating agarobiose units blinking between 3linked β-D-galactopyranosyl (G) and 4-linked 3,6-anhydro-α-L-galactopyranosyl (LA) units. The sulfate hemi esters and methyl esters in a variety of groupings and with a cyclic pyruvate ketal as 4,6-O-[(R)-1-carboxyethylidene] acetal are modified by substitution of hydroxyl groups in *Author for correspondence: .Department of Environmental Sciences, Sind Madressatul Islam University, Karachi, Pakistan. Arysta Life Sciences, Pakistan.