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Role of pharmacoscintigraphy in evaluating the presence of bioactive compounds in natural products,with particular reference to honey

Gaurav Mittal, Krishna Chuttani, Thakuri Singh, Nitin Kumar

Pharmacoscintigraphy, a nuclear medicine technique based on tracing the path of a radiolabeled drug/formulation to study its kinetics and biodistribution in the body is only a recent advancement. In the present work, role of pharmacoscintigraphy in evaluating the presence of bioactive molecules in natural products has been studied. Honey, one of the most widely used natural products with well established antibacterial properties was specifically used as an example for the study.Amethod of radiolabeling the aqueous extract of honey with γ-emitting technetium-99m (99mTc) was standardized in the laboratory. The radiolabeled preparationwas evaluated for radiochemical purity, stability and tissue distribution using tracer technique. The blood kinetics data in rabbits after intravenously administering 37MBq of 99mTc-labeled honey preparation exhibited a biphasic blood clearance pattern characterized by a fast half-life i.e., T1/2(f) of 25 ± 2.3 min and a slow half-life i.e., T1/2(s) of 16.7 ± 1.2 h. Subsequently, an animal model was prepared with localized Staphylococcus aureus (2 × 107 cells) infection in the thighmuscle ofNewZealandWhite rabbits. The presence of bioactive antibacterial compounds in the radiolabeled preparation was confirmed by its localization at the site of bacterial lesion and its subsequent detection by nuclear medicine scintigraphy (T/NT1.92 ± 0.03 at 24 h). In vivo stability of the radiolabeled preparation was further confirmed in 2 healthy human volunteers by taking dynamic scintigraphy images of the GIT region under Gamma camera after oral administration of the preparation. The work suggests that components of natural/herbal products can be radiolabeled with stability similar to other radiopharmaceuticals. We propose that pharmacoscintigraphy can therefore be used as an important tool for high throughput screening of natural products for the presence of bioactive molecules, thereby providing a method for screening useful from the non useful compounds. This will effectively result in rapid detection of promising leads for product development from the enormous potential offered by our natural product resources.