Q.From the following secondary metabolites which one is used as cardiac tonic ?

Digoxin, a Digitalis-derived cardiac glycoside, is the secondary metabolite used as a cardiac tonic.

Digoxin belongs to a class of plant secondary metabolites called cardiac (cardenolide) glycosides, obtained from the leaves of Digitalis purpurea and related foxglove species. It acts directly on heart muscle by inhibiting the Na+/K+-ATPase pump, which increases intracellular calcium and strengthens the force of cardiac contraction (a positive inotropic effect), while also helping to control heart rate in arrhythmias such as atrial fibrillation -- this is precisely why it is described as a 'cardiac tonic' in traditional pharmacognosy terminology. The other listed secondary metabolites serve entirely different medicinal purposes: capsaicin (from Capsicum/chillies) produces the pungent, …

Nilavembu (Andrographis paniculata) is the medicinal plant known as the King of Bitters.

Andrographis paniculata is an intensely bitter-tasting medicinal herb widely used in Siddha and Ayurvedic traditional medicine systems, most famously as the key ingredient of Nilavembu Kudineer, a herbal decoction promoted in Tamil Nadu for managing fever, including during dengue and viral fever outbreaks. Its extreme bitterness, attributed to diterpenoid lactone compounds such as andrographolide, is the basis for its common English epithet 'King of Bitters,' and its Tamil name, Nilavembu, is the name under which it is grown and marketed across South India. Holy basil (Ocimum tenuiflorum, Tulsi) is valued for its aromatic, adaptogenic and antimicrobial properties rather than extreme bitt …

Vinca rosea (Catharanthus roseus) is the anticancer medicinal plant among the options.

Catharanthus roseus, commonly called Vinca rosea or periwinkle, is a well-known medicinal plant whose leaves contain over a hundred terpenoid indole alkaloids, most notably vincristine and vinblastine. These two alkaloids interfere with microtubule formation during mitosis, arresting rapidly dividing cancer cells, and are used clinically to treat leukaemias, Hodgkin's and non-Hodgkin's lymphomas and certain solid tumours -- making Vinca rosea one of the most cited examples of a plant-derived anticancer drug source in botany syllabi. In contrast, Basmati is simply a premium long-grain aromatic rice cultivar valued for its cooking quality and export value; Marmelosin is a furocoumarin compound isolated from Aegle marmelos …

Santonin, the classic anthelmintic drug, comes from Artemisia maritima.

Artemisia maritima (also called Artemisia cina, commonly known as worm-seed) yields santonin, a sesquiterpene lactone extracted from its unopened flower heads. Santonin has been widely used as an anthelmintic (vermifuge) drug to expel intestinal roundworms (ascariasis) in traditional and early modern medicine. Pyrethrum (an …

Vilvam / bael = Aegle marmelos.

Aegle marmelos (Rutaceae), known as vilvam in Tamil and bael in Hindi, is a medium-sized tree whose ripe fruit pulp is used to prepare a cooling drink and as a remedy for digestive disorders (diarrhoea, dysentery), and whose leaves are used in Shaivite worship. Acaly …

Black nightshade = Solanum nigrum.

Solanum nigrum (manathakkali in Tamil) is a common weedy herb of the Solanaceae whose leaves and berries are traditionally used medicinally (e.g. as a hepatoprotective and anti-inflammatory remedy). It is commonly traded/marketed under the English name 'black nightshade'. The other opti …