Link to study : https://www.medrxiv.org/content/10.1101/2021.04.27.21256221v1.full.pdf
Here's a small (72 hospitalized patients), but well-designed (randomized, placebo-controlled) study on a mixture of three herbal remedies to reduce the symptoms of covid. The three plants used were 0.5 gram black myrobalans, 1 gram mastic, 1.5 grams sugarcane, given in powdered form twice a day and held under the tongue. The placebo group got powder made from bran and barley powder so that it looked the same. Probably the sugar in the treatment group would be a dead giveaway, for anyone who understood what was being tested. But at least the groups are randomized.
The results were that those receiving the herbal remedies had a faster resolution of cough, fever, difficulty breathing, and muscle aches. There was no statistically significant difference in oxygen saturation. The most interesting result though, was that the CRP levels came down faster in the treatment group than in the control group. CRP is an inflammatory marker that is high in people with the most severe forms of covid. Serum CRP is a more objective thing to measure than are cough or muscle aches.
They found a statistically significant decrease in the average time to release from the hospital (4 days vs 8 days). There were three deaths, all in the control group, but with such a small study, this was not statistically significant.
Most drugs we use now were originally found in plants, so it would make sense to try to extract and standardize the bioactive compounds in these plants. It looks like something in them is having a strong anti-inflammatory effect that is helping patients hospitalized with covid. Powdered plants can vary from batch to batch, and it sounds like this particular mixture is difficult to give to patients, as one person in the treatment group dropped out due to the taste of the stuff, and the researchers noted that patients became nauseous if they swallowed it instead of holding it under their tongues. Still, these are promising results that deserve further investigation.
Here is another graph, showing CRP levels:
