It is not uncommon that drug concentrations show optimum incremental effect at low concentration show decreasing response at increasing concentration becoming a type of diminishing returns. Reaching a plateau where no response is seen and then becoming inhibitory in their net addition response giving a bell response to concentration curve.

Iso thiocyanates are known to give this type of curve and are know in significant quantities in moringa.

In pharmacy there is a saying that the concentration maes the poison. The same compound with is toxic at a high concentration can have stimulatory effects a low concentrations.

If botanicals are used a low concentrations for marked effects their benefit is maximized in relation to cost.

Over application is a danger in all these treatments and more is not always better as many people think.

I agree with Mr Hepperly, I assume you have determined MIC for moringa solution against E coli, but can not reach minimum cidal concentration (the concentration that prevents E. coli growth completely) to the same microbial load. It is critical to fix the microbial load and gradually increase the concentration. Other reason is perhaps due to isothiocyanates that undergo hydrolysis in aqueous solution and the presence of bacterial cells at different pHs may accelerate the degradation rate.

Isothiocyanates in the Moringa extract might be responsible for such a response.

It seems that the Moringa active ingredients have definitely an obliterate/ stressful effect againist E coli.

Thank you!