Kuthuru Suresh’s favorite structure is:

Andrographolide-Salicylic acid pharmaceutical cocrystal

AP-SLA cocrystal

Source: Kuthuru Suresh, N. Rajesh Goud, and Ashwini Nangia., Chem. Asian J., 2013, 8, 3032 – 3041

Why?

Bitter pill: Andrographolide the bioactive agent used in traditional medicine in China, India, and South Asian countries. It is derived from the plant leaves of Andrographis paniculata . The local plant name in India is Kalmegh. A significant drop in the bioavailability of Andrographolide is due to transformation to its metabolite namely 14-deoxy-12-(R)-sulfo andrographolide isolated from humans and rats. The bioactive agent andrographolide was screened with pharmaceutically acceptable coformers to discover a novel solid form that will solve the chemical instability and poor solubility problems of this herbal medicine. Liquid-assisted grinding of andrographolide with GRAS (generally regarded as safe) coformers in a fixed stoichiometry resulted in cocrystals with vanillin(1:1), vanillic acid (1:1), salicylic acid (1:1), resorcinol (1:1), and guaiacol(1:1). All the crystalline products were characterized by thermal, spectroscopic, and diffraction methods. Interestingly, even though the cocrystals are isostructural, their physicochemical properties are quite different. The andrographolide–salicylic acid cocrystal completely inhibited the chemical transformation of andrographolide to its inactive sulfate metabolite, and the cocrystal exhibited a three times faster dissolution rate than pure andrographolide. This is a rare example of a pharmaceutical cocrystal that resists the chemical transformation that would otherwise make the drug inactive.—Kuthuru Suresh

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