Instrumental Methodology for Crystallinity Analysis of Herbal Drugs and Formulations

The crystallinity of pharmaceuticals possesses a vital role in their solubility, dissolution, bioavailability, stability, and therapeutic activity. Crystalline materials exhibit well-defined structures, specific melting points, optical properties, and other thermal properties. In contrast, amorphous materials possess a disordered structure that exhibits multiple chemical properties. In herbal formulations, crystallinity analysis is important for analyzing the quality of active ingredients (plant extract/enriched fraction/bioactive compound) and excipients used in the formulation. Crystallinity greatly affects the properties of pharmacokinetics and pharmacodynamics. The crystallinity of a herbal product may change over time due to the interaction of the herbal drug/extract/bioactives with the excipients. Hence, crystallinity analysis is important for ensuring consistent physicochemical attributes and therapeutic performance. Various instrumental methods are available to analyze the crystallinity of herbal products. These include X-ray diffraction (XRD), differential scanning calorimetry (DSC), polarized light microscopy (PLM), thermogravimetric analysis (TGA), dynamic vapor sorption (DVS), microcalorimetry, selected area electron diffraction (SAED), scanning electron microscopy (SEM), Raman spectroscopy, solid-state nuclear magnetic resonance (ssNMR), and hot stage microscopy. This chapter provides a detailed overview of these methods, their principles, applications, and advantages in the characterization of herbal drugs and formulations.