The Hydroalcoholic Extract of Uncaria tomentosa (Cat’s Claw)Inhibits the Infection of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) In Vitro

-e coronavirus disease 2019 (COVID-19) has become a serious problem for public health since it was identified in the
province of Wuhan (China) and spread around the world producing high mortality rates and economic losses. Nowadays, the
WHO recognizes traditional, complementary, and alternative medicine for treating COVID-19 symptoms. -erefore, we
investigated the antiviral potential of the hydroalcoholic extract of Uncaria tomentosa stem bark from Peru against SARSCoV-
2 in vitro. -e antiviral activity of U. tomentosa against SARS-CoV-2 in vitro was assessed in Vero E6 cells using
cytopathic effect (CPE) and plaque reduction assay. After 48 h of treatment, U. tomentosa showed an inhibition of 92.7% of
SARS-CoV-2 at 25.0 μg/mL (p < 0.0001) by plaque reduction assay on Vero E6 cells. In addition, U. tomentosa induced a
reduction of 98.6% (p 0.02) and 92.7% (p 0.03) in the CPE caused by SARS-CoV-2 on Vero E6 cells at 25 μg/mL and
12.5 μg/mL, respectively. -e EC50 calculated for the U. tomentosa extract by plaque reduction assay was 6.6 μg/mL
(4.89–8.85 μg/mL) for a selectivity index of 4.1. -e EC50 calculated for the U. tomentosa extract by TCID50 assay was 2.57 μg/
mL (1.05–3.75 μg/mL) for a selectivity index of 10.54. -ese results showed that U. tomentosa, known as cat’s claw, has an
antiviral effect against SARS-CoV-2, which was observed as a reduction in the viral titer and CPE after 48 h of treatment on
Vero E6 cells. -erefore, we hypothesized that U. tomentosa stem bark could be promising in the development of new
therapeutic strategies against SARS-CoV-2.