[Herbalogical study on historical evolution of collection, processing and efficacy of Citri Exocarpium Rubrum and Citri Grandis Exocarpium]

In ancient times, the original plants of Citri Exocarpium Rubrum and Citri Grandis Exocarpium had experienced succession and change, including tangerine(Citrus reticulata), pomelo(C. grandis), and Huazhou pomelo(C. grandis 'Tomentosa'), a specific cultivar of C. grandis produced in Huazhou, Guangdong. Before the Qing Dynasty, tangerine was the main original plant, while Huazhou pomelo came to the fore in the Qing Dynasty. In the 1950 s and 1960 s, the producing area of Huazhou pomelo was destroyed, and thus it had to be supplemented with pomelo. From then on, C. grandis 'Tomentosa' and C. grandis were both listed as the original plants of Citri Grandis Exocarpium in the Chinese Pharmacopoeia. This paper reviewed the historical evolution of the collection, processing, and efficacy of Citri Exocarpium Rubrum and Citri Grandis Exocarpium. The research showed that:(1)The harvest time of the original plants of Citri Grandis Exocarpium and Citri Grandis Exocarpium had changed from maturity to immaturity. The collection and processing of Citri Exocarpium Rubrum was first recorded in the Illustrated Classics of Materia Medica in the Song Dynasty. During the Ming and Qing Dynasties, the mesocarp of Citri Exocarpium Rubrum needed to be removed completely, and Citri Grandis Exocarpium from C. grandis 'Tomentosa' was processed into different specifications such as seven-piece, five-piece, and single piece. Furthermore, processed young fruits of Huazhou pomelo appeared.(2)Citri Exocarpium Rubrum and Citri Grandis Exocarpium were processed with carp skin for the first time in the Master Lei's Discourse on Medicinal Processing. It was suggested that carp skin might be helpful for eliminating bones stuck in throat. During the Song, Jin, and Yuan Dynasties, some other processing methods such as ba-king, stir-frying, and salt-processing appeared. Honey, soil, ginger juice, and alum were firstly used as adjuvants for the processing in the Ming and Qing Dynasties. Citri Exocarpium Rubrum was mainly prepared with salt in order to improve the effect of lowering Qi, while it was unnecessary for Citri Grandis Exocarpium from C. grandis 'Tomentosa' because of its obvious effect of lowering Qi and eliminating phlegm. The stir-frying and honey-frying methods helped reduce the strong effect of Citri Grandis Exocarpium from C. grandis 'Tomentosa'.(3)According to the application of Citri Exocarpium Rubrum and Citri Grandis Exocarpium in history, their medicinal use began in Han and Tang Dynasties, developed in Song, Jin, and Yuan Dynasties, and matured in Ming and Qing Dynasties. Citri Grandis Exocarpium from C. grandis 'Tomentosa' was originally applied in Ming and Qing Dynasties, and it still plays an important in role treating COVID-19 nowadays. Moreover, Citri Grandis Exocarpium from C. grandis had cold medicinal property, while Citri Grandis Exocarpium from C. grandis 'Tomentosa' had warm medicinal property, and thus they should not be treated the same. At present, Huazhou pomelo has a certain production scale. Therefore, it is recommended that in the next edition of Chinese Pharmacopoeia, only C. grandis 'Tomentosa' should be included as the original plant of Citri Grandis Exocarpium, and C. grandis should be deleted. The results are conducive to the further development and utilization of Citri Exocarpium Rubrum and Citri Grandis Exocarpium, and support the rational use of Citri Grandis Exocarpium and its processed products.