A product of the South American Cinchona calisaya tree, quinine\u2019s use as a preventive medicine has helped Europeans fight malaria since the 1400s. What began as a world-altering remedy, however, was turned into a commercialized, carbonated drink by 1858\u2014the naturally occurring compound is the key component to tonic water\u2019s bitter taste.\r\n\r\nWhile quinine\u2019s concentration in today\u2019s versions is no longer medicinal, its flavor remains essential. Sadly, the beverage became a cloying parody of itself in the 20th century, relying on synthetic quinine and artificial sugars. But the real stuff is back, now boosted by botanicals and other natural additives, and fizzing in a drink near you. Here\u2019s a look at some of the enhancements that complement the quinine and bubbles in modern tonics.\r\n\r\n\r\nSweeteners\r\n\u201cQuinine by itself is extremely bitter,\u201d says Lonnie Kahoe, sales analyst for Q Drinks, so tonics depend on a carefully calibrated sweetness to counteract its taste. Though many premium versions incorporate the fuller mouthfeel of cane sugars, Q Drinks utilizes the \u201cgently rounded sweetness\u201d of agave for its signature Q Tonic, which is made with quinine from Peru. \u201cIt gives a cleaner, earthy flavor that pairs well with botanical gins in a way that sugar doesn\u2019t,\u201d says Kahoe.\r\nCitrus\r\nAromatic tang from citrus zest is also a good complement to quinine. \u201cBitter orange provides zesty, fresh and sweet notes,\u201d says Tim Warrillow, co-founder of Fever-Tree, a drink company that\u2019s also striving to revive tonic waters. The company sources fruit from Mexico and lemon thyme from Provence. Another brand, Fentimans Botanically Brewed Beverages, uses oranges from the Mediterranean coast and ruby red grapefruit from the U.S.\r\nBotanicals\r\nGentle botanicals like elderflower and lemongrass lend additional depth, while some are more surprising. Myrtle and hyssop detract from bitterness in Fentimans Botanical Tonic Water, while marigold \u201cbrings a creamy, floral note\u201d to Fever-Tree\u2019s Indian variety. Also look for bottlings flavored with cardamom, ginger and rosemary.