Plants provided narcotics, sedatives, stimulants. Opium probably provided morphine and some other chemicals of interest. Recently Australian Society of Anaesthetists an exhibition at University of Sydeney, Australia (as reported in Nature vol 496 18th April, 2013). Literature spanning more than 5 centuries and illustrations document quest to alleviate pain and agony.
Our intellectuals of that time in east as well as west searched for plants to obtain chemicals for the same. Chinese, Ayurvedic, Kempo, Bhutanese, and Europeans documented plants and several well illustrated flora were produced in their primitive form but one would be surprised so see how accurate were the drawings. Alexander von Humoboldt from Germany, took a world wide tour to find out 'nature' and its treasure. Medical botany has in its root Opium poppy. English surgeon John Halle translated one of the most precious book from Latin to English and published it in 1565 which was based on 13th century surgical treatise Chirurgia parva.
Hills due to their topography and age in geological time scale have been greatest reservoirs of biodiversity and provided vast amount of plant sources which still make basis of drug formulations of modern day times. India has been known rich source of medicinal plants and the Rig Veda ( 5000 BC) mentioned 67, Yajurveda 81 and Atharvaveda ( 4500-2500 BC). mentioned 290 species of plants . Charak Samhita (700 BC) and Sushruta Samhita (200 BC) described the properties and uses of 1100 and 1270 plants respectively.
Duboisia hopowoodii was widely used by indigenous Central Australians as " stimulating narcotic" Its properties were reportedly similar to that of Stramonium sp which yielded alkaloid to relieve asthma and pain (German botanist Ferdinand von Miller worked on Duboisia and found similar properties) . Tylophora leaves are still used to relieve asthma and cough.
Ocimum sanctum is another plant of ancient times which still has value in home remedies. Glycirrhiza glabra roots are chewed to stop coughing and asthma. Australian plantations of Duboisia still supply 70 percent of the worlds alkaloid stocks of most widely used scopolamine and atropine. Atropa belladona has also been documented as source of atropine.
Reserpine is from plants and even in modern day medicine Taxol is obtained from plants So plants have long history healing ailments of man and there is need to dig deeper to find more.