Physico-rheological characterization of organically derived seed samples from Alpinia nigra (Gaertn.) B.L. Burtt, an ethnic medicinal plant of Northeast India

Alpinia nigra (Gaertn.) B.L. Burtt is one of the most easily available culinary items as well as medicinal plants of Northeast (NE) India. Physico-rheological characterization of the colloidal seed extracts of A. nigra and an isolated compound molecule, labdane diterpene-(E)-labda-8 (17), 12-diene-15, 16-dial- is carried out in the current study. Ideally, studies on the rheological or physical properties (which are important for industrial application) of plant derived secondary metabolites are lacking. In this context, the present study has been taken up. The optimum seed-to-solvent ratio for maximum yield of seed extracts is found to be 1:6. Contact angle value indicates the hydrophobicity of these plant samples; labdane diterpene being the most hydrophobic. All the samples exhibit specific rotation and hence, optical behavior. The DSC results suggest the lack of crystallinity of the samples; the compound exhibits the characteristic behavior of diterpenes like drimenol, cninin etc. The plant extracts and compound show a high degree of thermal stability. The viscosity of the samples shows an increasing trend with concentration but a decreasing trend with temperature; labdane diterpene exhibits the highest viscosity at all temperatures. The results obtained provide interesting insight towards the application of the A. nigra-derived extracts in the food and pharmaceutical industries.