冰片（分子式：C10H18O），又名片脑、桔片、龙脑香、梅花冰片、羯布罗香、梅花脑、冰片脑、梅冰、龍腦、瑞脑、腦子、天然冰片、老梅片、梅片等，是由2个异戊二烯结构单元组成的环状化合物，属于单萜衍生物[1]。根据旋光性分为左旋龙脑和右旋龙脑[2]。右旋龙脑主要来源于龙脑樟和阴香树[3]，而左旋龙脑主要来源于菊科植物[4]。
冰片的合成前体由细胞质中的甲羟戊酸途径和质体中的4-磷酸-2-甲基赤藓糖途径产生的异戊烯基焦磷酸和二甲基烯丙基焦磷酸合成[5]。在香叶基焦磷酸合酶的催化作用下，这些合成物缩合生成香叶基焦磷酸[6]，随后在二磷酸龙脑合酶的作用下环化成二磷酸龙脑，最终在碱性磷酸酶的作用下脱去磷酸基团生成龙脑[2]。此外，龙脑在龙脑脱氢酶的催化作用下被氧化成樟脑[7]。
冰片极易被氧化成酮而生成樟脑，人工合成方法是通过Meerwein–Ponndorf–Verley还原反应将樟脑还原成冰片。加入硼氢化钠可以加快反应速率，使反应成为不可逆反应，这是由于动力学控制反应产物为异冰片。
冰片被认为具有抗菌、保护心脑血管、镇痛消炎、防止血栓、促进药物透过血脑屏障等多种作用[8]。常应用于临床治疗，作为止痛剂、镇痛剂和麻醉剂[9]。
冰片具有剂量毒性，大量使用会引起毒性反应。[10]
Wang, Hong; Ma, Dongming; Yang, Jinfen; Deng, Ke; Li, Meng; Ji, Xiaoyu; Zhong, Liting; Zhao, Haiying. An Integrative Volatile Terpenoid Profiling and Transcriptomics Analysis for Gene Mining and Functional Characterization of AvBPPS and AvPS Involved in the Monoterpenoid Biosynthesis in Amomum villosum. Frontiers in Plant Science. 2018-06-20, 9. doi:10.3389/fpls.2018.00846. Chen, Changjie; Miao, Yuhuan; Luo, Dandan; Wang, Zixin; Guo, Lujuan; Zhao, Tingting; Liu, Dahui. Cloning and Functional Verification of the Borneol Dehydrogenase Encoding Gene AArBDH1 in Artemisia argyi. Chinese Bulletin of Botany. 2023-07-01, 58 (4): 560. doi:10.11983/CBB22123. Xingxing, Liu; Xi, Zhang; Xiali, Guo; Shangji, Gong; Xiangmei, Jiang; Yuxin, Fu; Liping, Luo. Multivariate Analyses of Volatile Chemical Composition in Leaves of Different Cinnamomum camphora Chemotypes. Chinese Bulletin of Botany. 2014, 49 (2): 161. doi:10.3724/SP.J.1259.2014.00161. Ho, Tsung-Jung; Hung, Chien-Che; Shih, Tzenge-Lien; Yiin, Lih-Ming; Chen, Hao-Ping. Investigation of borneols sold in Taiwan by chiral gas chromatography. Journal of Food and Drug Analysis. 2018-01, 26 (1): 348–352. doi:10.1016/j.jfda.2016.10.012. Hurd, Matthew C.; Kwon, Moonhyuk; Ro, Dae-Kyun. Functional identification of a Lippia dulcis bornyl diphosphate synthase that contains a duplicated, inhibitory arginine-rich motif. Biochemical and Biophysical Research Communications. 2017-08, 490 (3): 963–968. doi:10.1016/j.bbrc.2017.06.147. Ma, Rui; Su, Ping; Guo, Juan; Jin, Baolong; Ma, Qing; Zhang, Haiyan; Chen, Lingli; Mao, Liuying; Tian, Mei; Lai, Changjiangsheng; Tang, Jinfu; Cui, Guanghong; Huang, Luqi. Bornyl Diphosphate Synthase From Cinnamomum burmanni and Its Application for (+)-Borneol Biosynthesis in Yeast. Frontiers in Bioengineering and Biotechnology. 2021-02-11, 9. doi:10.3389/fbioe.2021.631863. Khine, Aye Aye; Lu, Pei-Chieh; Ko, Tzu-Ping; Huang, Kai-Fa; Chen, Hao-Ping. Cloning, expression, identification and characterization of borneol dehydrogenase isozymes in Pseudomonas sp. TCU-HL1. Protein Expression and Purification. 2020-11, 175: 105715. doi:10.1016/j.pep.2020.105715.
有害 Xn
易燃 F
