# Compounds Isolated from Paepalanthus spp. (Eriocaulaceae) and Their Evaluation in Antimicrobial, Cytotoxic, and Antiviral Assays

## TL;DR

This study isolated compounds from two Paepalanthus species and tested their antimicrobial, cytotoxic, and antiviral effects, finding some potential activity against cancer and bacteria.

## Contribution

The paper reports the isolation and biological evaluation of new compounds from Paepalanthus spp. with potential antimicrobial and antiviral properties.

## Key findings

- 6-methoxykaempferol showed antimicrobial activity against S. aureus with a MIC of 250 μg mL–1.
- 6-methoxykaempferol-3-O-β-D-6″-(p-coumaroyl)-glucopyranoside inhibited ZIKV enzyme NS2B-NS3pro at 1.95 μM.
- The compounds showed limited cytotoxicity but up to 29.17% growth inhibition in colon cancer cells.

## Abstract

Paepalanthus acanthophyllus and P. bromelioides belong to the
Eriocaulaceae family.
According to the literature, secondary metabolites isolated in Paepalanthus have interesting biological activities. This
research aimed to isolate constituents from the capitula of the mentioned
species and to evaluate their cytotoxic, antimicrobial, and antiviral
activities. Through maceration and several types of separation procedures,
the crude extracts were produced, and the structures of constituents
were identified mostly by nuclear magnetic resonance. Cytotoxic and
antimicrobial activities were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium
bromide and 2,3,5-triphenyl-2H-tetrazolium chloride
methods, respectively, while antiviral activity was evaluated by enzymatic
and phenotypic assays. Two flavonoids were isolated in the dichloromethane
fraction, and four flavonoids and one benzoic acid derivative were
isolated in the ethyl acetate fraction of P. acanthophyllus. Paepalantine was isolated from P. bromelioides. The isolated compounds did not show significant cytotoxicity, and
the highest values of growth-inhibitory activity observed reached
29.17% (colon cancer) and 19.24% (breast cancer). Antimicrobial evaluation
showed the best result to 6-methoxykaempferol against S. aureus (MIC = 250 μg mL–1). Antiviral evaluation showed that 6-methoxykaempferol-3-O-β-D-6″-(p-coumaroyl)-glucopyranoside
inhibited the ZIKV enzyme NS2B-NS3pro in the lowest micromolar range
(IC50 = 1.95 μM); however, it did not show inhibition
when evaluated in phenotypic assays with the ZIKV replicon.