The leaf extract has a definite action on blood; it markedly delays the clotting time. Action of this extract on blood plasma clotting time using the highly poisonous venom of the snake Russel’s viper as a standard was studied. Most effective injection of clotting was noticed on full saturation with ammonium sulphate. Insecticidal and insect repellent properties of neem have been justified.
Neem oil inhibited the growth of the following bacteria, causing important diseases: Mycobacterium tuberculosis (tuberculosis), Salmonella typhi (typhoid), Vibrio choleri (cholera) and Klebsiella pneumoniae (pneumonia). Even a ten per cent water extract of neem leaves has been found to possess antiviral properties viz action against viruses responsible for many diseases. Neem oil and two of its bitter principles nimbidin and nimbidol were studied for their antibacterial effects, with considerable success.
Nimbidin and sodium nimbidinate caused slowing of heart rate in frogs followed by missing of beats, partial heart block and finally cardiac arrest in diastole by directly depressing the cardiac muscle—an action that may be utilised in correction of the cardiac dysrhythmia (viz the upsets in the rhythms in the heart beat). Sodium nimbidinate is seen to be spermicidal (i.e. killing to sperms).
Nimbidol in a dose of 50 mg/Kg in rats caused immediate reduction in temperature. Nimbidin was found to be effective in various skin diseases such as furuncolosis, arsenical dermatitis, ulcers due to burns, Herpes labialis infection, scabies and seborrhoedic dermatitis. Nimbidin gargle and dentifrices have been found to be effective in the treatment of bleeding gums and pyorrhea.
Neem oil has been found to be a cerebral poisoning agent; therefore it has to be used with great caution in the treating of neurological troubles. However, it is interesting to note that in South India, there does exist the practice of anointing the body with neem oil and also give a little quantity of it orally to children when they suffer from fits.