Thesis (PhD) - Cyprus International University. Institute of Graduate Studies and Research Pharmaceutıcal Sciences

Scutellaria sibthorpii is an endemic plant of Cyprus and it is used in the treatment of
microbial infections, pains and inflammations. The powder leaf was extracted by
maceration in 80% methanol for 24 hours and then fractionated using n-hexane, ethyl
acetate and n-butanol. The crude extract and fractions were screened for the presence of
saponins, tannins, flavonoids and triterpenoids/steroids. Total phenolic and flavonoid
contents were determined using Folin–Ciocalteu’s reagent and aluminium chloride assays.
The chemical profiling of ethyl acetate fraction, n-butanol and the crude extract were
conducted by LC- MS/ LC-QTOF-MS based metabolomic profile analyses. The essential
oil was analysed by GC-MS and revealed the presence of monoterpenoids,
sesquiterpenoids and other compounds. The antioxidant activity was determined using
DPPH, hydrogen peroxide and β-carotene assays. Agar disk diffusion and micro broth
dilution methods were used for the antibacterial activity of the crude extract on
Pseudomonas aeruginosa and Legionella pneumophila. Gentamicin (10 μg) was used as a
positive control. The acute toxicity was determined using Lorke’s method. The analgesic
activity assayed using acetic acid-induced writhing, hotplate and formalin-induced
nociception. Anti-inflammatory activity was investigated by means of formalin-induced
acute inflammation. The antipyretic activity was studied using Brewer’s yeast. The crude
extract (CrESs)/fractions demonstrated antioxidant activity in all the models. The nhexane
fraction (HFSs) had the highest scavenging activity with IC50 of 2.944 m/mL in
the DPPH assay. In the H2O2 scavenging assay, the ethyl acetate fraction (EtFSs) had the
highest scavenging activity (IC50 of 0.4352 mg/mL) and in the β-carotene bleaching assay
with IC50 of 0.00014 mg/mL. Generally, the EtFSs had higher antioxidant activity when
compared with other test samples and with ascorbic acid (2.944 mg/mL-Hexane, 9.29
mg/mL-hydrogen peroxide and 2.85 mg/mL-β-carotene). The MIC of CrESs on
Pseudomonas aeruginosa and Legionella pneumophila were 0.15625±0.00 mg/mL and
0.3125±0.00 mg/mL respectively. The LD50 of the CrESs /fractions were greater than
5000 mg/Kg. The CrESs/fractions demonstrated analgesic activity but it was higher in
EtFSs when compared to piroxicam. The EtFSs showed higher anti-inflammatory activity
than piroxicam at the late hours. The antipyretic study revealed at 200 mg/Kg, EtFSs
fraction significantly reduced the rectal temperature of rats similar to paracetamol. The
findings of this research have validated the uses of Scutellaria sibthorpii in traditional
medicine as antibacterial, antioxidant, analgesic, anti-inflammatory and antipyretic.