n.natural bases containing nitrogen found in plants

1. Alkaloids are often extracted from plants and used in medicine for their analgesic and stimulant properties.
   生物堿通常從植物中提取，并因其鎮(zhèn)痛和興奮作用而在醫(yī)學中應用。
2. Some alkaloids, such as morphine and caffeine, have important medicinal uses, while others can be toxic.
   一些生物堿，如嗎啡和咖啡因，具有重要的藥用價值，而另一些則可能具有毒性。
3. The alkaloid quinine is used to treat malaria.
   生物堿奎寧用于治療瘧疾。
4. Nicotine, an alkaloid found in tobacco, is known for its addictive properties.
   煙草中的生物堿尼古丁以其成癮性而著名。