The Plectranthus ornatus, a creeping herb of the Lamiaceae family, is up to 0.5 m tall, with purple flowers, and succulent and oval leaves, and has a strong and penetrating aroma. It is distributed from 0 to 2200 masl and originates from Ethiopia-Tanzania, with various ethnobotanical uses. In Colombia, it is present in several departments, including Antioquia, Boyacá, Caldas, Cundinamarca, Nariño, Quindio, Santander, and Valle (Plectranthus Ornatus Codd, n.d.).
Pharmacological studies of P. ornatus have shown its antibiotic, anti-inflammatory, antioxidant, and cytotoxic effects on leukemia and lung cancer cells (Sitarek et al., 2022). The P. ornatus extract has also shown antioxidant capacity, mainly associated with compounds such as rosmarinic, caffeic, and o-hydroxycinnamic acids (Medrado et al., 2016).
Among the major compounds of the P. ornatus extract are trans β-caryophyllene, Caryophyllene oxide, β–Selinene, α–Selinene; these compounds are also found in essential oils such as Laurus nobilis and Ruda graveolens, and are associated with insect repellent action of great interest to the organic pharmaceutical industry (Katherine Mariely Peña, 2022). They are also associated with antibacterial power and are found in other species such as Cymbopogon giganteus and Moringa stenopetala (Fernandes et al., 2021). However, the easy propagation and adaptability to different thermal floors make P. ornatus a promising species for its production within pharmaceutical agriculture. Specifically, β-Selinene has shown its biocidal capacity (Chil-Núñez et al., 2018), and in previous studies, its potential for tick control has also been evaluated (Garcia Paz, 2011).
On the other hand, compounds such as trans β-caryophyllene, also present in P. ornatus, have marked antimicrobial activity against gram-positive Staphylococcus bacteria. aureus and Staphylococcus epidermidis; but low toxicity against Artemia salina (Mejía et al., 2012). Similarly, α-pinene has demonstrated its antimicrobial power against Grand negative bacteria (Farias et al., 2017), and antifungal capacity against Candida albicans (Silva & Fonseca, 2022). Finally, another of the compounds of interest present in P. ornatus is limonene, which has also been tested as a repellent and control metabolite against flies (Cosmo, 2011).
In the production of plants with pharmaceutical interest, a crop free of pesticides and under controlled conditions that guarantee the composition of the extracts is essential. Among the novel approaches are climate-smart agriculture, sustainable and regenerative intensification, integrated agricultural systems, integrated nutrient management, and biodynamic agriculture, among others. All these approaches include the implementation of novel practices for agricultural sustainability (Muhie, 2022).
Biodynamic agriculture is a method of organic agriculture that promotes diversified, resilient, and constantly evolving farms that can provide long-term ecological and economic benefits in production systems in developing countries. It includes practices such as composting, crop rotation, animal welfare, and understanding the farm as an organism that can allow the protection of the environment and quality of life for farmers (Turinek et al., 2009).
Biodynamic practices have been gaining popularity, particularly in Europe where farmers empirically affirm that farms with biodynamic management increase sustainability and improve crop quality. However, scientific validation is necessary to demonstrate these assertions, particularly in the use of biodynamic preparations such as 500 and 501 (Rienth et al., 2023). Furthermore, biodynamic agriculture maintains a close relationship between the General Anthroposophical Society in Switzerland and agricultural practice through a spiritual and cosmological worldview (Wright, 2022).
Several studies suggest that biodynamic agriculture can provide benefits not only for the environment but for the entire farm in general. However, further research is necessary to provide more information to stakeholders (Santoni et al., 2022). In addition to using the common tools in organic production, biodynamic agriculture involves adapting compost through the use of biodynamic preparations which are sprayed at low concentrations but have an effect on soil microbial biomass, respiration, and mineralization. In short, they make the soils more biotically active (Carpenter-Boggs, 2015). Using biodynamic preparations in soils has allowed for the improvement of their physical-chemical characteristics and microbial function (Rodas-Gaitan et al., 2022).
Composts with biodynamic preparations have shown higher temperatures in the active composting stage, higher amounts of nitrate, higher enzymatic activity, and a higher ratio of bacteria to fungi (Reeve et al., 2010). Other substrate types, such as sandy mixtures, have reported properties such as aeration, drainage, and water retention that can optimize plant cultivation (Aguirre, 2019), as well as greater germination rates, with percentages close to 84% (Mendez Natera et al., 2009). The chemical and biological properties of newspaper/horse manure compost suggest that this compost could be used as an alternative to peat-based compost and could provide a technology to utilize large amounts of waste paper (Ball et al., 2000).
Therefore, the aim of this study is to evaluate a substrate made from biodynamic compost in comparison to other substrates used in organic production, such as sandy mix, vermicompost, and horse compost, to determine if there are significant differences in the optimization of biomass and metabolite composition in the cultivation of Plectranthus ornatus.