Therefore, a massscale clinical trials and specic documentation on its molecular mode of action is needed.Based on the aforementioned background, the present chapter describes the documentation of important medicinal plants and their derived bioactive principles, potential to combat important human diseases with underlying mode of action to facilitate A.It is estimated around of the drugs launched worldwide and more than population of the developing countries basically rely on plant products for their preliminary health care or as a supplement for health. According to WHO, it has been estimated that, species of plants exist on the earth, up to now, only around or, plants have been used as medicines by humans to treat these complications.In spite of their appreciated potential against different human diseases, their exploration as medicine directly to human has faced several challenges due to lack of scientic and clinical evidence regarding their biochemical mode of action on particular cells, tissues, or organs as well as standardization issues.Based the aforementioned background, the present chapter deals with exploration of some important medicinal plants for the development of drugs, which are useful for treatment of severe humans ailments.The knowledge of thousands of years of traditionally used herbal medicines can be used to overcome several medical problems of present generations.The development of medicine for the early humans was not an easy task; several of them have sacriced their lives during the course of testing of plants with some benecial medicinal importance.Some plants might be poisonous, harming their lives.Medicinal plants are the major source of traditional medicines as well as some modern medicines.It comprises of four elements: monarch, minister, assistant, and servant according to their roles in the formula.Unani medicine is also recognized by WHO as alternative medicine system for curing the sufferers.The body temperature of a human being shows its wellbeing and mental and physical status.Alteration in the body temperature makes the human body susceptible to many kinds of diseases.The traditional medicine system is well integrated in the scheme of national healthcare system of the country and well organized. The other two, SE and SY are called kidney and pancreas types, respectively. Plants have several secondary metabolites in the form of phytochemicals which protects plants from invasion of pests and infection from microorganisms.These phytochemicals have some active ingredients which can be used in the form of drug for the treatment and prevention of disease. Phenolic compounds of plants are most valuable among the secondary metabolites because of their active role in morphological development, reproductive process, and physiological responses.There are about structures of different plant phenolic compounds known to us.The central skeleton of phenolic compounds is formed by one phenolic ring, and hydrogen is replaced by more active residues like hydroxyl, acetyl, and methyl groups.This is the reason behind wide spectrum of biological properties of phenolic compounds.In plants, these phenolic compounds are assembled in phenolic rings and are called polyphenols. Phenolic compounds containing plants have high antioxidant properties.Plants absorb the radiation of sun and produce oxygen as a byproduct.Oxygen gets activated by UV light and heat generated by sunlight and produces reactive oxygen species, which interfere with cellular entities and alter them leading to cellular damage.