British crops: growing conditions and sustainability

For instance, the British plants pot marigold (Calendula officinalis)1 and St John’s wort (Hypericum perforatum)2 both have European Medicines Agency (EMEA) monographs supporting use for symptomatic treatment of minor inflammations of the skin (such as sunburn). Both are used in cosmetics for their soothing properties.3 White horehound (Marrubium vulgare) and betony (Stachys officinalis), both members of the mint family (Labiatae) are also listed in the CosIng database as skin conditioning/ soothing and skin protecting respectively. Both these herbs were mentioned in the Leech Book of Bald, an Anglo-Saxon book of remedies4 thought to have been written around 1000. Both herbs were recommended for many diverse ailments, and while the inclusion of betony in a “…good drink against all temptations of the devil” might seem worryingly obscure, as suggested by Thomas (2011) further research might support at least some of the Leech book usages. For conditions such as inflammation and pruritis where pharmaceutical and personal care interests meet, research regularly delivers new data on native British plants including those with traditional use, often with evidence pointing to specific active constituents. It was recently reported that iridoids such as aucubin could be responsible for at least part of the antiinflammatory activity of Stachys species such as betony,5 and the diterpene marrubiin which is a main ingredient in Marrubium vulgare was reported to have significant antiphlogistic activity.6 Knowledge of the active constituents can point the way to novel preparation methods for optimising herbal extracts for personal care applications and an IP position. The examples above include a number of plants that to our knowledge are not cultivated in the UK, although they grow wild. The exception is Calendula which has been grown in the UK (although on a small acreage) for its seed oil. A number of other speciality seed oil plants have been cultivated in the UK including borage for GLA (gamma-linolenic acid), Echium for stearidonic acid and Camelina.7 Plants grown for their aromatic properties and essential oils include peppermint, spearmint, lavender, rosemary, chamomile and lemon balm. The cultivation and processing of rosemary for its antioxidant products including carnosic acid has been evaluated in the context of a LINK project8 with collaborators including Boots-Alliance and Croda International. The British climate will also support the cultivation of plants from other similar temperate zones, and while climate change presents threats to growers it may also provide future opportunities for the introduction of crops more suited to warmer, drier growing conditions.9 Medicinal plants currently grown commercially in the UK include Narcissus species for the alkaloid galanthamine, opium poppy and cannabis, the two former in the field and the last species under glass. Field trials of Artemisia annua as a source of artemisinin, an antimalarial sesquiterpene lactone have also taken place in the UK in the context of a LINK project.10

Beyond the field – protected crops and tissue culture

The diversity of species for personal care applications that can be grown in the UK could of course be widened enormously by including protected (e.g. glasshouse) crops. While there may be a cost benefit to growing plants in the field, protected cultivation can provide advantages afforded by greater control over growing conditions, delivering reliability of yield and uniformity of product. Furthermore, while potentially energy-intensive, glasshouse crops can be cultivated very sustainably. An outstanding example is the 18 ha greenhouse at Wissington which uses recycled heat and CO2 from the British Sugar sugarbeet processing factory, plus collected rainwater for irrigation to grow 140 million tomatoes a year.11 Significantly for the personal care industry, in glasshouses, IPM (Integrated Pest Management) techniques that avoid or significantly reduce the use of pesticides can be successfully applied. IPM is an environmentally sensitive approach to pest management that involves setting thresholds for taking action, then monitoring pests and putting in place preventative measures and effective controls when needed. A typical IPM pest control method would involve the release of mites that predate upon insect pests, with pesticides only ever being employed as a last resort. For new or unusual crops, IPM strategies can also avoid potential issues around the use of chemical crop protection products, where specific chemicals must be registered for use with specific plant species. Because crops for personal care are generally grown on a small scale, their use does not provide sufficient market size for the companies owning crop protection products, to justify pursuing the legislative approval necessary to add such species to the label recommendations. Hydroponics takes the concept of quality control to another level where plants are grown in nutrient solutions, without soil. Temperature, lighting, humidity and nutrient regimes can be very tightly controlled if carried out in a glasshouse, and both horizontal and vertical systems are feasible, the latter maximising utilisation of space. A LINK project with partners including Boots Company plc, ADAS UK Ltd and Universities of Leeds and Exeter laid the foundations for a commercial production process, with marshmallow (Althaea officinalis) roots being harvested from a nutrient film hydroponic cultivation.12 Marshmallow has a use in personal care products to reduce the erythema associated with sunburn and other skin complaints, with polysaccharides being some of the active soothing components. A key finding from the LINK project was that plants grown hydroponically produced large numbers of fine roots compared with soil-grown plants which had much larger and tougher roots. Commercial roots were variable in quality, requiring extensive washing, and there is a general concern in the industry that wild-crafted roots can be contaminated with heavy metals and pesticides. The fine roots from hydroponic cultivation (Fig. 4) were easier to process and had higher levels of polysaccharides than soil-grown roots as well as a different profile of phenolics. Furthermore, when aqueous extracts of hydroponically-grown and commercial samples of marshmallow root were tested in a number of in vitro assays, extracts from hydroponically-grown roots had superior activity in protecting human lung and skin fibroblasts against UVA-induced DNA damage, and in reducing membrane lipid peroxidation.13 Perhaps the ultimate technology aimed at producing clean, uniform raw materials is plant cell culture whereby suspensions of plant cells are grown under strictly controlled, sterile conditions. There have been a number of commercial-scale processes but one of the best-known is based at Phyton Biotech GmbH in Germany. Here, huge bioreactors of thousands of litre volumes grow cultures of the yew tree (Taxus) that produce paclitaxel, a natural anticancer drug widely used for the treatment of ovarian and other cancers. High capital equipment costs have meant that the technology is economically feasible for only the highest value products such as pharmaceutical drugs. However, recently a cosmetics ingredients company announced their acquisition of a 600 L bench wave system bioreactor which they are using for the production of a plant cellbased cosmetic ingredient.14 The ‘vessel’ of this bioreactor produced by GE Healthcare is a sterile disposable bag and this design could simplify some of the technical complexities often associated with largescale plant cell culture, as well as reducing costs. While plant cell cultures are versatile and can produce very high yields of certain biologically active metabolites such as rosmarinic acid (with yields of more than 20% w/v reported from Coleus cell cultures15) as well as novel chemical structures not found in the whole plant, they are limited in their production of certain chemical classes such as essential oils. In the whole plant these are produced and accumulated in glandular trichomes, highly specialised cellular structures that are not found in cell suspension cultures. Cell culture is an expensive strategy for production of personal care ingredients and needs to be justified by (for example) relatively high yield of an active metabolite compared with that of the whole plant. There are currently no large scale plant cell culture operations in the UK, but there is laboratory-scale expertise, and the wave system bioreactor may make the approach more accessible.