Tier 2 — strong

Quercetin–bromelain supplementation and clinical outcomes of COVID-19: a randomized, double-blind, placebo-controlled trial in hospitalized patients in Tunisia

Marwa Gargouri, Héla Gargouri, Jihen Jedidi, Naoures Issaoui, Imen Ketata, Houda Ghorbel, Leila Zrelli, Hajer Azouzi, Mohamed Ali Boukhchina
BMC Pharmacology and Toxicology 2026 Online publication; article/page identifier not supplied in the verified metadata

Bibliography

DOI
10.1186/s40360-026-01257-2
Funding
Support was acknowledged from the Ministry of Health and the Ministry of Higher Education and Scientific Research of Tunisia.
Competing interests
The authors declare no competing interests.

Study snapshot

DesignRandomized double-blind placebo-controlled hospitalized COVID-19 trial
ModelHuman intervention research
Sample244 adults
InterventionQuercetin 800 mg/day for 10 days then 400 mg/day for 30 days, with bromelain; each capsule contained 400 mg quercetin and 100 mg bromelain
Duration40 days of scheduled supplementation
EndpointsEvents and survival

What the study showed, in plain terms

Published in 2026, this source examined immunity and respiratory health. Design: Randomized double-blind placebo-controlled hospitalized COVID-19 trial. Sample/model: 244 adults. The exposure or intervention was Quercetin 800 mg/day for 10 days then 400 mg/day for 30 days, with bromelain; each capsule contained 400 mg quercetin and 100 mg bromelain. Follow-up or treatment period: 40 days of scheduled supplementation.

Respiratory deterioration was less frequent with the combination; mortality and hospital-stay differences were not significant.

Combination effects cannot be assigned to quercetin. Registration was retrospective, subgroup findings were exploratory, and the publisher displayed a peer-reviewed accepted version subject to further edits.

Continue with Quercetin Data Center

For topic-level interpretation, read Quercetin for Immune Health, Colds and COVID-19. This is a related guide; the citation panel separately identifies articles that directly cite this paper.

Key findings

  • Respiratory deterioration was less frequent with the combination; mortality and hospital-stay differences were not significant.
  • The recorded outcome domains were Events and survival.
  • The result applies to the tested exposure: Quercetin 800 mg/day for 10 days then 400 mg/day for 30 days, with bromelain; each capsule contained 400 mg quercetin and 100 mg bromelain; 40 days of scheduled supplementation.

What this study can and cannot tell us

  • Combination effects cannot be assigned to quercetin. Registration was retrospective, subgroup findings were exploratory, and the publisher displayed a peer-reviewed accepted version subject to further edits.
  • An individual controlled trial must be interpreted alongside its comparator, sample size, endpoint selection and independent replication. It does not validate a different commercial formulation or a general longevity claim.
  • Source basis: Source check: publisher abstract and bibliographic metadata. Missing method details, funding information or participant denominators are not inferred.

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Citation network

Articles citing this research paper

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Editorial review

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Dr. Khaled Mahmoud, MBBChCritical Care Medicine, Longevity Science & Editorial Direction Dr. Amr Yasser, PhDCardiometabolic, Musculoskeletal, Gut & Bioavailability Dr. Abdulla Mostafa, PhDCellular Senescence, Neurological, Mitochondrial & Brain-Ageing Biology