The 21st century is witnessing a war between mankind and microorganisms.
The worldwide outbreak of infectious diseases is responsible for morbidity and
mortality. The pharmaceutical industry has limited drugs in the pipeline against
infectious diseases. Resistance of microorganisms against already available drugs is
another concern. An initiative from researchers to search for new ways to prevent or
treat infectious diseases is necessary. Many herbal drugs are known to be effective
against pathogenic organisms from ancient times. Repurposing of herbal medicines for
infectious diseases is a prodigious initiative. Azadirachta indica, commonly known as
neem, is known to be effective against infectious diseases from ancient times. It is a
member of the Meliaceae family. Leaves, seeds, fruits, and roots of this plant are
reported to be effective according to Chinese, Ayurvedic, and Unani medicine. The
plant has antiviral, antibacterial, and antifungal properties. The principal component of
neem is azadirachtin. Other constituents, namely nimbolinin, nimbin, nimbidin,
nimbidol, are also known to be having medicinal properties. Antibacterial and
antifungal properties can be attributed to azadirachtin, quercetin, ß-sitosterol, gedunin,
and polyphenolic flavonoids. Many pharmacological studies report antimicrobial
efficacy of Azadirachta indica. The present chapter will explain the link between
phytochemical constituents of neem to antimicrobial activity along with possible
underlying mechanisms and pathways. Clinical studies on neem are also discussed in
great detail to highlight the emergence of this traditional medicine into modern
medicine in the battle against infectious diseases.
Keywords: Antibacterial, Antifungal, Antimalarial, Antiviral, Azadirachta indica,
Azadirachtin, Meliaceae, Neem, Nimbin, Quercetin, Salannin.
