Emerging Green Excipients for the Pharmaceutical Industry

Excipients are substances or mixtures of substances used in the formulation of a drug. Defined as being inert with respect to the active ingredient, and not inducing any undesirable effects in the patient (with the exception of excipients with notorious effects), they are chosen for technological reasons (to stabilize, facilitate flow, improve taste...) or biopharmaceutical reasons (to solubilize, modulate release...). These raw materials, essential for the formulating pharmacist, are governed by legislation and listed in the European Pharmacopoeia.

Excipients come from a variety of sources: mineral or organic, synthetic or natural. Excipients of natural origin have been used since the beginnings of formulation in the 2nd century. Some were extracted from plants: vegetable oils, starches, etc. With industrialization in the 19th century, some were replaced by synthetic or hemisynthetic excipients derived from petrochemicals: mineral oils, silicones, modified celluloses, etc. But environmental concerns have led to a renewed interest in raw materials of natural origin that are more respectful of the environment. The agri-food and cosmetics formulation sectors were the first to be affected, and the changes they triggered led to the emergence of raw materials whose potential in the pharmaceutical field now needs to be assessed and developed to meet pharmaceutical requirements.

Plant-derived excipients offer a number of advantages: firstly, their abundance on land or in the oceans, and secondly, their safety. They are virus-free, generally biocompatible and biodegradable, ensuring no accumulation in the body or the environment. Disadvantages include their purity, variable composition from batch to batch, the risk of bacterial contamination in the case of hydrated products, and the fact that certain excipients of plant origin can be allergenic (gluten, peanuts).

Excipients of plant origin have different chemical functions depending on their lipid, protein or polysaccharide nature. Their functions are manifold: gelling, emulsifying, coating, binding, solubilizing, etc. They can be classified into two categories: technological functions, which help with formulation or administration, and patient acceptability, and biopharmaceutical functions, which improve absorption of the active ingredient into the body and/or modulate its release rate. Whatever their role, excipients, often multiple within a single formulation, appear in all pharmaceutical forms: tablets and capsules, suppositories, solutions, emulsions, suspensions, aerosols, patches... These excipients must be safe, easily identifiable by conventional analytical techniques, and chemically inert to avoid interactions with other excipients, active ingredients and packaging.

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