Meroterpenoids are secondary metabolites formed due to mixed biosynthetic pathways which are produced in part from a terpenoid co-substrate. These mixed biosynthetically hybrid compounds are widely produced by bacteria, algae, plants, and animals. Notably amazing chemical diversity is generated among meroterpenoids via a combination of terpenoid scaffolds with polyketides, alkaloids, phenols, and amino acids. This review deals with the isolation, chemical diversity, and biological effects of 452 new meroterpenoids reported from natural sources from January 2016 to December 2020. Most of the meroterpenoids possess antimicrobial, cytotoxic, antioxidant, anti-inflammatory, antiviral, enzyme inhibitory, and immunosupressive effects.

A novel reversible AIE + ESIPT probe, myricetin, easily obtained from vine tea, for detection and imaging of O₂^•−.

Fluorescence-based on-site and long-term sensing and bioimaging of biomarkers are highly desired for effective diagnosis. Aggregation-induced emission luminogens (AIEgens) with excited-state intramolecular proton transfer (ESIPT) characteristics have outstanding advantages in biological applications due to their large Stokes shift and low background signal in the aggregate state. However, most of the reported AIEgens are fabricated through rational design and complex synthesis procedures. Importantly, with rich structural skeletons and ease of access, natural products have superiority in developing promising AIEgens with ESIPT. Here, hyperoside(quercetin-3-O-β-galactoside) has been easily obtained from Hedyotis diffusa. After the incubation of hyperoside with β-galactosidase (β-Gal), the hydrolysis product, hydrophobic quercetin, is aggregated in situ, which presents AIE and ESIPT characteristics with a large Stokes shift (170 nm). Then, a novel light-up fluorescent probe has been fabricated for the detection of β-Gal with a good linear relationship (0.03–12 U mL⁻¹), high sensitivity (a detection limit of 0.013 U mL⁻¹) and superior selectivity. Meanwhile, excellent biocompatibility, low cytotoxicity, outstanding photostability, and good intracellular retention demonstrate its superiority for on-site and long-term (about 8 h) imaging of β-Gal in SKOV-3 cells. The results demonstrate the application of hyperoside in the sensing and imaging of β-Gal in biological samples, and propose the great possibility of natural products for developing novel AIE-based fluorescence probes.

In this work, flavonoid fraction from the leaves of Crataegus pinnatifida was separated into its seven main constituents using a combination of HSCCC coupled with pre-HPLC. In the first step, the total flavonoid extract was subjected to HSCCC with a two-solvent system of chloroform/methanol/water/n-butanol (4:3:2:1.5, v/v), yielding four pure compounds, namely (–)-epicatechin (1), quercetin-3-O-(2,6-di-α-l-rhamnopyranosyl)-β-d-galactopyranoside (2), 4′′-O-glucosylvitexin (3) and 2′′-O-rhamnosylvitexin (4) as well as a mixture of three further flavonoids. An extrusion mode was used to rapidly separate quercetin-3-O-(2,6-di-α-l-rhamnopyranosyl)-β-d-galactopyranoside with a big K_D-value. In the second step, the mixture that resulted from HSCCC was separated by pre-HPLC, resulting in three pure compounds including: vitexin (5), hyperoside (6) and isoquercitrin (7). The purities of the isolated compounds were established to be over 98%, as determined by HPLC. The structures of these seven flavonoids were elucidated by ESI-MS and NMR spectroscopic analyses.