In the 1990s, Pfizer took the lead in developing and listing the world's first non-gelatin capsule shell product, the main raw material of which is the cellulose ester "hydroxypropyl methyl cellulose" from plants. Because this new type of capsule does not contain any animal ingredients, it is praised by the industry as a "plant capsule". At present, although the sales volume of plant capsules in the international capsule market is not high, its development momentum is very strong, with broad market growth space.
　　
"With the development of medical science and technology and related sciences, the importance of pharmaceutical excipients in the production of pharmaceutical preparations has gradually been recognized, and the status of pharmacy is increasing." Ouyang Jingfeng, an associate researcher at the Chinese Academy of Chinese Medical Sciences, pointed out that pharmaceutical excipients not only determine the quality of new dosage forms and new preparations of drugs to a considerable extent, but also help the preparation to form, stabilize, solubilize, increase solubilize, extend release, sustained release, controlled release, orientation, timing, positioning, quick-acting, efficient and long-acting, and in a sense, the development of an excellent new excipient can lead to the development of a large class of dosage forms, improve the quality of a large number of new drugs and preparations, and its significance far exceeds the development of a new drug. In the pharmaceutical dosage forms such as cream pills, tablets, injections, and capsules, capsules have become the main dosage forms of oral solid preparations because of their high bioavailability, improving the stability of drugs, and timed positioning and release of drugs.

At present, the main raw material for the production of capsules is gelatin, gelatin is made by hydrolysis of animal bones and skins, and is a biological macromolecule with a ternary spiral structure, with good biocompatibility and physical and chemical properties. However, gelatin capsules also have certain limitations in application, and the development of new materials for capsule shells of non-animal origin has become a hot spot in the recent research of pharmaceutical excipients. Wu Zhenghong, a professor at China Pharmaceutical University, said that because of the "mad cow disease" in European countries such as britain, France and the Netherlands in the 1990s (including Japan in Asia, which also found mad cows with mad cow disease), the people of Western countries had a strong distrust of beef and cattle-related by-products (gelatin is also one of them). In addition, Buddhists and vegetarians are also resistant to gelatin capsules made from animal raw materials. In view of this, some foreign capsule companies began to study new materials for capsule shells of non-gelatin and other animal sources, and the dominance of traditional gelatin capsules began to waver.

Finding new materials to prepare non-gelatin capsules is the current development direction of pharmaceutical excipients. Ouyang Jingfeng pointed out that the raw materials of plant capsules are currently hydroxypropyl methylcellulose, modified starch and some hydrophilic polymer food glues, such as gelatin, carrageenan, xanthan gum and so on. Hydroxypropyl methyl cellulose capsules have similar solubility, disintegration and bioavailability to gelatin capsules, while having some advantages that gelatin capsules do not have, but the current application is still not very extensive, mainly because of the high price of the product, compared with gelatin, hydroxypropyl methyl cellulose capsule raw material cost is higher, in addition to the slow gel speed, resulting in a long production cycle.

In the global pharmaceutical market, plant capsules are one of the fastest growing products. Wu Zhenghong said that compared with gelatin capsules, plant capsules have the following obvious advantages: First, there is no crosslinking reaction. Plant capsules have strong inertness and are not easy to crosslink with aldehyde groups or other compounds. The second is suitable for water-sensitive drugs. The moisture content of plant capsules is generally controlled between 5% and 8%, and it is not easy to chemically react with the contents, and the lower water content ensures the stability of the hygroscopic contents that are susceptible to moisture. The third is good compatibility with the main pharmaceutical excipients. Vegetable capsules have good compatibility with lactose, dextrin, starch, microcrystalline cellulose, magnesium stearate and other major commonly used pharmaceutical excipients. The fourth is to have a more relaxed filling environment. Plant capsules have relatively loose requirements for the working environment of the filled contents, whether it is the requirements for the working environment or the pass rate on the machine, which can reduce the cost of use.
　
　
"In the world, plant capsules are still in their infancy, only a very few enterprises can produce plant medicinal capsules, and it is necessary to further strengthen research in production processes and other aspects, while also increasing market promotion efforts." Ouyang Jingfeng pointed out that at present, the output of gelatin capsules in China has reached the first place in the world, while the market share of plant capsule products is still low. In addition, because the process principle of producing capsules has not changed for more than a hundred years, and the continuous improvement of equipment is designed according to the production process of gelatin, how to use the process and equipment for preparing gelatin capsules to prepare plant capsules has become a focus of research, which involves the specific study of process elements such as viscosity, rheological properties and viscoelasticity of materials.　
　　

Although it is not possible for plant capsules to replace the dominance of traditional gelatin hollow capsules, plant capsules have obvious competitive advantages in China's traditional Chinese medicine preparations, biological preparations and functional foods. Zhang Youde, a senior engineer at the School of Materials Science and Engineering of Beijing Institute of Technology, believes that with people's in-depth understanding of plant capsules and the transformation of the public's drug concept, the market demand for plant capsules will grow rapidly.