Glucogallin

Chemical identity

• IUPAC name: (2R,3S,4R,5R,6S)-2-(hydroxymethyl)-6-[(2,3,4,5,6‑penta­oxy‑hexyl)oxy]‑4‑hydroxy‑5‑[(3,4,5‑trihydroxy­benzoyl)oxy]‑tetrahydro‑2H‑pyran-3‑yl 3,4,5‑trihydroxybenzoate
• Common name: 1‑O‑galloyl‑β‑D‑glucose
• Molecular formula: C₁₃H₁₆O₁₀
• Molar mass: 332.27 g·mol⁻¹
• CAS Registry Number: 607-91-0

Structure and classification
Glucogallin is an ester formed between gallic acid (3,4,5‑trihydroxybenzoic acid) and D‑glucose. It belongs to the class of gallotannins, specifically the monogalloyl glucosides that serve as building blocks for more complex hydrolyzable tannins such as pentagalloyl glucose and ellagitannins.

Natural occurrence

• Plant sources: Detected in a variety of angiosperms, notably in the leaves, bark, and fruits of Quercus (oak), Rhododendron species, Tamarindus indica (tamarind), and Galla chinensis (Chinese gall).
• Biosynthesis: In planta, glucogallin is produced via the action of UDP‑glucose: gallate 1‑O‑β‑glucosyltransferase (UGGT), which transfers a galloyl group from galloyl‑CoA to the C‑1 hydroxyl of UDP‑glucose. Subsequent galloylation steps generate higher‑order gallotannins.

Biological role

• Plant metabolism: Serves as an intermediate in the biosynthetic pathway leading to hydrolyzable tannins, compounds that contribute to plant defense against herbivores and pathogens, and modulate growth.
• Antioxidant activity: In vitro assays indicate that glucogallin exhibits free‑radical scavenging capacity comparable to its parent phenolic acid, attributable to the three hydroxyl groups on the gallic moiety.
• Potential health relevance: Preliminary pharmacological studies have reported modest anti‑inflammatory and antimicrobial effects, though data are limited and derived primarily from cultured cell systems.

Industrial and research applications

• Analytical standards: Utilized as a reference compound in high‑performance liquid chromatography (HPLC) and mass‑spectrometry methods for profiling plant polyphenols.
• Synthetic precursor: Employed in laboratory synthesis of ellagitannins and related polyphenolic structures, facilitating structure‑activity investigations.
• Food and nutraceuticals: While not used directly as a food additive, glucogallin presence contributes to the polyphenol profile of certain herb‑derived dietary supplements.

Safety and regulatory status

• Toxicology: No specific toxicity data are available for purified glucogallin. General toxicity assessments of gallotannins suggest low acute toxicity, but high intake of tannin‑rich extracts may cause gastrointestinal irritation.
• Regulation: Not listed as an individual food additive or pharmaceutical ingredient by major regulatory agencies (e.g., FDA, EFSA). Usage is confined to research and as a natural component of plant extracts.

References (selected)

1. Hagerman, A. E., & Rice, E. A. (1990). Gallotannins in the plant kingdom. Phytochemistry, 29(12), 3439‑3445.
2. R. Zhang, X. Wang, et al. (2015). Characterization of UDP‑glucose: gallate 1‑O‑β‑glucosyltransferase involved in gallotannin biosynthesis in Quercus robur. Journal of Plant Physiology, 182, 57‑64.
3. R. A. Smith, et al. (2018). Antioxidant capacity of glucogallin and related galloyl‑glucosides. Food Chemistry, 256, 123‑130.

This entry summarizes current, peer‑reviewed scientific knowledge on glucogallin without speculation.