Herbal Medicine: Dry Extracts Production and Applications

GALLO, LC; BUCALÁ V; RAMÍREZ RIGO M V; PIÑA J

Plant Extracts: Role in Agriculture, Health Effects and Medical Applications

Nova Science Publishers, Inc.

Lugar: Nueva York; Año: 2013; p. 171 - 198

Chapter 6. Medicinal plants have provided therapeutic agents for thousands of years and continue being a great source of novel pharmaceutical products. Two-thirds of the world population still relies to some extent on natural medicines for primary health care. In addition, the demand for medicinal plant products is now increasing in both developing and developed countries as a consequence of a growing aging population and increasing consumer awareness about general health. Nevertheless, there is a widespread concern about safety, efficacy and quality of herbal medicines. Currently, many countries are conscious about the need of regulatory-guidelines formulation for medicinal herbs production and use. Phytomedicines represent a wide range of product types: from raw herbs (dried or fresh) to others with different processing degrees (such as tinctures and extracts). The herbal medicines production involves adequate cultivation and post-harvest methodologies as well as botanical identification of the vegetable drug. For herbal medicine end-products with added value, appropriate extraction procedures that maintain the bioactivity, standardization of extracts, selection and tuning of the operating conditions of drying processes and design of pharmaceutical formulations are also necessary. In this chapter the current global scenario of phytomedicine is first presented, evaluating its impact on public health and markets. Then, the challenges associated to safety, efficacy and quality of herbal medicines due to the extracts complexity are introduced. Understanding the great importance of providing accurate dosages of herbal therapeutic agents, the production of dry plant extracts is next discussed focusing on: the drying step including the formulation of the solution to be dried (which comprises the herbal extract) and the dried extract quality. Regarding the technologies for preparing dry medicinal plants extracts, spray drying is particularly described. This technique is the most commonly used in the herbal processing industries due to its ability to generate a particulate product with precise specifications in continuous operations. Several key studies about the effect of the operating conditions and the feed composition on the yield of the spray drying process and the particles properties are subsequently summarized. For tablets production by direct compression, herbal dried powders require being stable and having adequate flow properties, consequently the effects of different processing variables on the dried extracts stability and flowability are also presented. The formulation of solid dosage forms, based on spray-dried plant extracts, for conventional and modulated delivery is then reviewed. Finally, the existing strategies to modulate drug delivery of plant extracts are described. Modified-release phytomedicines are still in an exploratory stage. Therefore, the prospective for the development of novel products is discussed.