الفهرس 
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Abstract
The present study aimed to assemblage of algal flora from different water sources in Siwa Oasis (one of the Egyptian desert oases), determination of some physico-chemical and biological parameters for the collected water samples and studying their relation to the distribution and species composition of microalgal communities, isolation and purification of some common microalgal taxa from the collected water samples in this oasis as a natural source for therapeutic application. Studying their phytochemical constituents, determination of carbohydrates, proteins and vitamin E (α-tocopherol) concentrations. Also, studying the antibacterial effect against some infectious human pathogenic bacteria and the antioxidant activity of their extracts and finally analyzing the main bioactive components of the most potent algal extracts.
Water samples were collected during summer 2014 from five stations in Siwa Oasis:
A Ain Cleopatra B Haudh Cleopatra
C Ain Fetnas D Fetnas Lake
E The private farm’s well
1- Determination of the Physico-chemical parameters for the sampling water stations in Siwa Oasis:
Temperature:
Temperature values showed that water temperatures were warm, recorded 29 oC at all sampling stations.
pH:
pH values in most of the water samples were on the alkaline side, recorded the highest value of 7.8 at station E and the lowest value of 7.3 at station D.
Electrical Conductivity (EC):
Values of electrical conduction in the most valuable recorded samples were high especially at station D which registered value of 44500 μmhos /cm and the lowest registered value of 3200 μmhos /cm at station E.
Dissolved Oxygen (DO):
Dissolved oxygen values ranged from 4.9 mg/l at station B and 6.6 mg/l at station D.
Total Dissolved Solids (TDS):
TDS recorded values ranged between 2533 mg/l at station E and 28100 mg/l at station D.
Chlorides (Cl):
The highest values of chlorides 24709 mg/l at station D and the lowest value 1140.4 mg/l at station E.
Calcium (Ca):
Calcium values recorded range of values between 478.0848 and 4598.58 mg/l at stations E and D; respectively.
Magnesium (Mg):
Magnesium registered values ranged between 48.41 and 2788.828 mg/l at stations E and D; respectively.
Total Hardness:
Total Hardness registered values ranged between 1393.89 and 25929.90 mg/l at stations E and D; respectively.
Sodium (Na):
The present study recorded sodium value ranged between 350.5 and 4755 mg/l stations E and D, respectively.
Potassium:
Potassium values recorded the lowest value among all dissolved salts, varied between 16 and 206 mg/l at stations E and D, respectively.
Carbonate [CO3—] and bicarbonate [HCO3-]:
The carbonate values at the all stations were completely depleted. Bicarbonate concentrations values at the all sampling stations recorded value of 244 mg/l at all stations except at station D which recorded the highest value of 549 mg/l.
Heavy metal:
The results showed that the concentration levels of the all studied thirteen heavy metals are within the permissible limits of the World health organization (WHO, 2006) except for B. Boron (B) was detected at the stations C and D, the recorded value of 4.438 ppm at the station D exceeded the permissible limit (0.3 ppm) but the recorded value of 0.1558ppm at the station C didn’t exceed. Aluminium)Al) and Iron (Fe) were detected only at the station E, the recorded value of 0.0598 ppm for )Al) didn’t exceed the permissible limit (0.2 ppm), also the recorded value of 0.0567 ppm for (Fe) didn’t exceed the permissible limit (0.3 ppm),
Determination of some biological parameters for the water sampling stations in Siwa Oasis:
The phytoplankton composition:
The present results showed a remarkable diversity of phytoplankton communities. 54 species have been identified which belonging to 35 genera and represented by 4 groups: Bacillariophyta, Cyanophyta, Chlorophyta and Euglenophyta.
Bacillariophyta:
Bacillariophyta was the most common groups found in all collected samples, it occupied the first predominant group. Totally 20 taxa were recorded. It was the most numerous in Ain Fetnas.
Cyanophyta:
The predominance of Cyanophyta was nearly the same as that of Bacillariophyta group, it occupied the second predominant group. Totally 19 taxa were recorded. It was the most numerous in Ain Cleopatra.
Chlorophyta:
Chlorophyta occupied the third predominant group. Totally 13 Chlorophyta taxa were recorded. It was complete depleted in Fetnas lake.
Euglenophyta:
Euglenophyta group occupied the fourth predominant group, it was rarely present in the study area. Only 2 taxa were recorded. It was complete depleted in Haudh Cleopatra.
Determination of the growth parameters for the three isolated microalgae:
Pigment content:
The highest value of Chlorophyll (a) (2.40 µg/ml) was recorded for Chlorella vulgaris, while the lowest values were recorded for chroococcus turgidus (0.67 µg.ml–1) and for Phormidium tenue (0.53 µg.ml–1).
The only recorded value of Chlorophyll (b) was 2.57 µg/ml for the green alga Chlorella vulgaris.
The highest value of Carotenoid (2.07 µg/ml) was recorded for Chlorella vulgaris, while the lowest values were recorded for chroococcus turgidus (0.3 µg.ml–1) and for Phormidium tenue (0.2 µg.ml–1).
Dry weight:
The recorded value of dry weight was 0.26 g/l for Chlorella vulgaris and was 0.46 g/l for chroococcus turgidus, while for Phormidium tenue was 0.38 g/l.
Preliminary qualitative phytochemical screening of the three isolated microalgae:
The phytochemical analysis of the extracts of Chlorella vulgaris, chroococcus turgidus and Phormidium tenue showed the presence of carbohydrates, proteins, sterols, terpenoids, cardiac glycosides, phenolics, flavonoids and saponins but absence of alkaloids, anthraquinone and tannins.
Quantitative determination of the total carbohydrates content:
The highest total carbohydrate value of 31gm/100gm was recorded for Chlorella vulgaris which was nearly the same that recorded for Phormidium tenue (30.8 gm/100gm), while for chroococcus turgidus was 14.2 gm/100gm.
Quantitative determination of the total proteins content:
The highest total protein value of 28.4gm/100gm was recorded for Phormidium tenue, while the lowest values were recorded for Chlorella vulgaris (11.6gm/100gm) and for chroococcus turgidus (11.9 gm/100gm).
Quantitative determination of vitamin E (α-tocopherol) using (HPLC):
The results showed that the three tested isolated microalgae Chlorella vulgaris, chroococcus turgidus and Phormidium tenue contained vitamin E (α-tocopherol) with different concentrations. The highest value of 145.7 ppm was recorded for Chlorella vulgaris, while the lowest value of 12.6 ppm was recorded for Phormidium tenue.
Biological activity:
Antibacterial activity of the total methanolic extracts for the the three isolated microalgae:
Phormidium tenue methanolic extract showed the strongest antibacterial effect. It affected on five of selected tested pathogenic bacteria with different diameters of inhibition zone including one Gram-positive bacteria Staphylococcus aureus (27mm) and four Gram-negative bacteria Salmonella typhi (a gastrointestinal tract (GIT) infectious bacteria) (30mm), Acinetobacter baumannii (28mm), Klebsiella pneumonia (18mm) and Escherichia coli (17mm). Recorded results of inhibition zone diameters of chroococcus turgidus methanolic extract revealed that it affected on two Gram-ve pathogenic bacteria only, Salmonella typhi (27mm) and Acinetobacter baumannii (17mm). Recorded results of inhibition zone diameters for Chlorella vulgaris methanolic extract revealed that it affected on two pathogenic bacteria only, one was Gram +ve Staphylococcus aureus (19mm) and the other was Gram -ve Salmonella typhi (26mm).
Antioxidant measurement of the the total methanolic extracts for the the three isolated microalgae:
The results showed that the methanolic extracts of the three tested isolated microalgae Chlorella vulgaris, chroococcus turgidus and Phormidium tenue showed moderate antioxidant activity. The highest scavenging percentage value of 60.9% was recorded for Phormidium tenue, while the lowest value of 40% was recorded for Chlorella vulgaris.
Antibacterial activity of the successive extracts for Phormidium tenue:
The Phormidium tenue isolate which gave the promising antibacterial activity. The ethyl acetate successive extract for Phormidium tenue showed the strongest antibacterial effect. It recorded the maximum diameter of inhibition zones against Enterococcus sp. (23mm) and the gastrointestinal tract (GIT) infectious bacteria Salmonella typhi (20mm). It was the only one that affected Acinetobacter baumannii (26mm), Klebsiella pneumonia (21mm) and Staphylococcus aureus (15mm), also it affected on Escherichia coli with diameter of inhibition zone (20mm). While other pathogenic bacteria were resistant to it.
The growth of Escherichia coli, Enterococcus sp.and Salmonella typhi was inhibited by using petroleum ether successive extract and recorded inhibition zones of 23 ,22 and 19 mm, respectively. While other pathogenic bacteria were resistant to it.
All tested pathogenic bacteria were resistant to the 80% methanol successive extract of Phormidium tenue except Escherichia coli which recorded inhibition zone of 15 mm and also all tested pathogenic bacteria were resistant to the water successive extract of Phormidium tenue.
Chromatographic analysis of the ethyl acetate successive extract for Phormidium tenue:
According to some chromatographic investigations it was found that the phenolic acids were the main active compounds of the ethyl acetate successive extract of Phormidium tenue. Separation and determination of the phenolics were performed using HPLC technique. It resulted in identification of 21 phenolic compounds which were ethyl vanillate, catechein, alpha-coumaric acid, epicatachin, chlorogenic acid, 4-amino-benzoic acid, pyrogallol, cinnamic acid, coumarin, ellagic acid, p-OH- benzoic acid, ferulic acid, caffeic acid, Iso-ferulic acid, protocatchuic acid, 3,4,5-methoxy-cinnamic acid, p-coumaric acid, gallic acid, salycilic acid. catechol and vanillic acid with different concentrations ranging between 1755.2 to 6.778 μgg-1 for ethyl vanillate and vanillic acid compounds; respectively.