Evaluation of Biological Activity of Turkish Plants. Rapid Screening for the Antimicrobial,Antioxidant, and Acetylcholinesterase Inhibitory Potential by TLC Bioautographic Methods

Using thin-layer chromatography (TLC) bioautography, a total of 58 extracts from various organs (aerial parts, leaves, flowers, fruits, roots) of 16 Turkish plants were tested for their antibacterial, antifungal, acetylcholinesterase inhibitory, antioxidant, and radical scavenging activities. The hexane, CHCl₃/CH₂Cl₂, water, and total MeOH extracts were used. No activity was observed against two Gram-negative bacteria (Escherichia coli and Pseudomonas aureginosa) and the yeast Candida albicans. However, 23 plant extracts, mostly the CHCl₃/CH₂Cl₂ and H₂O-solubles, inhibited the growth of all five Gram-positive bacteria tested, Micrococcus luteus, Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, and Staphylococcus epidermidis. Of the active extracts, the CHCl₃-soluble of the roots of Putoria calabrica (L. fil) DC (Rubiaceae) displayed the highest antibacterial potential. The majority of the CHCl₃/CH₂Cl₂ crude extracts also appeared to inhibit acetylcholinesterase on TLC plates at 100 µg/spot concentration. Particularly active samples were the middle polarity extracts (CHCl₃/CH₂Cl₂) of the leaves of Rhododendron smirnovii Trautv., R. ponticum L., and R. ungernii Trautv. (Ericaceae). β-Carotene, β-carotene/linoleic acid mixture, and 2,2-diphenyl-l-pieryhydrazyl (DPPH) solutions sprayed onto TLC plates were used for detecting antioxidant and radical scavenging properties of the crude extracts. Antioxidant and radical scavenging activities were found to be predominant in highly polar extracts. The water-solubles of all Rhododendron (Ericaceae) and Phlomis (Lamiaceae) species presented the most significant activity.