An important drug used for the treatment of malaria – Quinine is extracted from

The correct option is Brak of Cinchona.

Detailed Explanation:
Quinine is a naturally occurring chemical compound known as an alkaloid, which has historically been the primary drug used to prevent and treat malaria, a life-threatening disease caused by Plasmodium parasites transmitted through the bites of infected female Anopheles mosquitoes.

Quinine is extracted from the bark (spelled as "brak" in the options) of the Cinchona tree. The Cinchona genus consists of large shrubs or small trees that are native to the tropical Andean forests of western South America. The medicinal properties of the bark were discovered by the indigenous peoples of Peru and Bolivia, who used it as a muscle relaxant to prevent shivering caused by cold. It was later introduced to Europe in the 17th century, where its efficacy in treating malaria fevers was recognized.

Let us look at why the other options are incorrect:
• Red ants: Red ants are known for producing formic acid, which they use for defense, but they do not produce quinine.
• Calyx of cinnamon: Cinnamon is obtained from the inner bark of trees belonging to the genus Cinnamomum. While it is widely used as a spice and in traditional medicine, it does not contain quinine.
• Brak of tulsi: Tulsi (Holy Basil) is a revered medicinal herb in Ayurveda used for respiratory and immune support, but it is not the source of the anti-malarial drug quinine.