How effective is eucalyptus-based treatment for curing COVID-19 (or coronavirus in general)?

Question

According to The Jakarta Post, (Indonesia's) Agriculture Ministry claims to have developed eucalyptus-based COVID-19 treatment:

The Agriculture Ministry has developed a eucalyptus-based treatment that it claims has been shown to reduce the transmission of COVID-19. The ministry expects it to play a role in the fight against the virus.

The ministry announced the treatment on Friday (8 May 2020), saying it was based on lab tests conducted by agricultural researchers.

Agriculture Minister Syahrul Yasin Limpo said the treatment had been tested on influenza as well as beta and gamma coronaviruses and was able to kill 80 to 100 percent of the viruses.

The Ministry’s Health Research and Development Agency (Balitbangtan) has developed a few prototypes of the medication in the form of inhalers, roll-ons, ointment, balms and diffusers.

[...]

The ministry’s Health Research and Development Agency head Fajry Jufry said the product had shown “very good results” after being tested on COVID-19 patients, adding that the ministry was waiting for approval from related parties to distribute it.

Fajry said the antiviral medication was identified through agency research on various herbs and remedies, such as ginger, guava, temulawak (Curcuma) and essential oils.

However, the test result is not public, and no real evidence if the result is positive or not.

Are there any other credible tests regarding eucalyptus-based treatment for COVID-19, or even for diseases by coronavirus in general?

Answer 1

There is actually a preprint (meaning not yet peer reviewed) paper on this, which at least identifies the active compound they say has the anti-viral properties, so it is in the (fairly usual) pharmacology realm in this (first glance) respect. But what I found is a just an in silico study, so if this is all there is, it's probably a bit premature for them to start "dishing it out".

Eucalyptol (1,8 cineole) from Eucalyptus Essential Oil a Potential Inhibitor of COVID 19 Corona Virus Infection by Molecular Docking Studies

the main viral proteinase (Mpro/3CLpro) has recently been regarded as a suitable target for drug design against SARS infection due to its vital role in polyproteins processing necessary for coronavirus reproduction.Objectives: The present in silico study was designed to evaluate the effect of Eucalyptol (1,8 cineole), a essential oil component from eucalyptus oil, on Mpro by docking study.Methods: In the present study, molecular docking studies were conducted by using 1-click dock and swiss dock tools. Protein interaction mode was calculated by Protein Interactions Calculator. Results: The calculated parameters such as RMSD, binding energy, and binding site similarity indicated effective binding of eucalyptol to COVID-19 proteinase.

The 3CLpro of Covid-19 is being targeted by other drugs being investigated. So this is not something outlandish, but I have no idea how safe that compound is at the concentrations required for effective anti-viral action. Wikipedia says it could be toxic at some concentrations. So probably more research would be prudent.

A quick search also find an older study from China on the compound and its effect on the infectious bronchitis virus. The latter study involved some more "real world" experiments including a MMT assay, and evaluated cytotoxicity relative to ribavirin, but it's still what would be considered preclinical investigation.