No abstract

Caffeic acid (CA) is a naturally occurring plant-derived polyphenol possessing diverse biological properties. However, the poor water-solubility of CA restricts its widespread applications. On the other hand, biogenic amines such as spermine and spermidine are natural constituents in eukaryotes. In this work, we present water-soluble complexes of CA with spermine and spermidine by exploiting the acid-base interaction. Four different compositions have been prepared by varying the CA to amine ratios, whose chemical structures have been probed in detail using Fourier-transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR) studies that have revealed the acid-base interaction between the constituent precursors. The obtained acid-base complexes at their native pH values have shown enhanced antibacterial and antioxidant activities than pristine CA. Further, the CA-polyamine complexes have shown high anticancer performances in the concentration range that is compatible with the normal cell lines.

Caffeic acid (CA), an edible plant-derived polyphenol, is known for its various beneficial characteristics such as antimicrobial, antioxidant, and anti-inflammatory. Recently, our group reported a facile acid–base complexation of CA with dopamine (Dopa) to circumvent its poor water solubility. Despite the promising biological characteristics of the CA–Dopa complex, Dopa is permitted only for intravenous but not for oral administration. In the present study, to harness the advantages of CA toward nutraceuticals and food preservatives, we prepared complexes of CA with basic amino acids such as histidine and arginine. The edible as-prepared CA–amino acid complexes have been characterized using FT-IR, UV–visible, and 1H, 13C, and 2D 1H–1H NOESY NMR spectroscopic studies. In addition to the antibacterial activity against Escherichia coli and Staphylococcus aureus, the complexes have also shown high antioxidant characteristics as ascertained by 2,2′-azino-bis­(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) assay. Further, the in vitro cytotoxicity and superoxide dismutase studies over the mouse fibroblast cells have signified the biocompatibility and radical scavenging performance of the complexes. Finally, the α-amylase assay has shown non-interference of the CA–amino acid complexes in the metabolic function of the enzyme, and thereby proving their potential as edible additives in the pharmaceutic, food, and agro sectors.

The use of terminal deoxynucleotidyl transferase for the first time in a mechanistic explorationthrough colorimetric sensing and isothermal titration calorimetric studieshas provided direct experimental evidence of boronic acid moiety bridging...