Effects of Lichen Metabolites Atranorin, Lobaric Acid, and Usnic Acid on Growth and Biomass of Rocket (Eruca sativa Mill.) Microgreens

Abstract

Microgreens are young, nutrient-rich seedlings that have gained considerable attention for their high nutritional value and short cultivation period. This study investigated the effects of three lichen-derived secondary metabolites – atranorin, lobaric acid, and usnic acid – at five different concentrations (2, 4, 6, 8, and 10 mg/L) on the growth and biomass parameters of Eruca sativa Mill. microgreens, specifically shoot length, root length, and fresh and dry weight. Morphological observations indicated that germination began on the third day, and seedlings reached the typical microgreen stage with fully expanded cotyledons and dark green true leaves by the eighth day. Results revealed that all three metabolites exhibited a dose-dependent response pattern. Atranorin and lobaric acid showed optimal stimulation of shoot and root growth at moderate concentrations (4–6 mg/L), while usnic acid demonstrated maximum growth promotion at higher doses (8–10 mg/L). Low concentrations (2 mg/L) generally caused mild inhibitory effects on elongation and biomass accumulation. Heatmap and clustering analyses confirmed two distinct response groups: low-dose inhibition and mid-to-high-dose stimulation. These findings suggest that lichen metabolites can act as potential natural biostimulants for microgreen cultivation when applied at appropriate concentrations, supporting sustainable and environmentally friendly production systems.

Keywords

• Atranorin
• Eruca sativa
• growth stimulation
• lichen secondary metabolites
• lobaric acid
• microgreens
• usnic acid

References

1. Bačkor M, Hudá J, Repčák M, Ziegler W, Bačkorová M. 1998. The influence of pH and lichen metabolites (vulpinic acid and (+)-usnic acid) on the growth of the lichen photobiont Trebouxia irregularis. Lichenologist. 30(6):577–582.
2. Bhaswant M, Shanmugam DK, Miyazawa T, Abe C, Miyazawa T. 2023. Microgreens—a comprehensive review of bioactive molecules and health benefits. Molecules. 28(2):867.
3. Demirci Z, Dogan M, Emsen B. 2025. The effect of soaking durations on fenugreek seeds (Trigonella foenum-graceum L.) for microgreen production. Int J Adv Nat Sci Eng Res. 9(2):104–110.
4. Dubey S, Harbourne N, Harty M, Hurley D, Elliott-Kingston C. 2024. Microgreens production: exploiting environmental and cultural factors for enhanced agronomical benefits. Plants. 13(18):2631.
5. Ebert AW. 2022. Sprouts and microgreens—novel food sources for healthy diets. Plants. 11(4):571.
6. Emsen B. 2019. The antioxidant and antigenotoxic potential of Peltigera canina and Umbilicaria nylanderiana based on their phenolic profile. Farmacia. 67(5):912–921.
7. Galanty A, Paśko P, Podolak I. 2019. Enantioselective activity of usnic acid: a comprehensive review and future perspectives. Phytochem Rev. 18(2):527–548.
8. Górka B, Lipok J, Wieczorek PP. 2015. Biologically active organic compounds, especially plant promoters, in algae extracts and their potential application in plant cultivation. In: Marine Algae Extracts: Processes, Products, and Applications. p. 659–680.

9. Graziani G, Cirillo A, Giannini P, Conti S, El-Nakhel C, Rouphael Y, Di Vaio C. 2022. Biostimulants improve plant growth and bioactive compounds of young olive trees under abiotic stress conditions. Agriculture. 12(2):227.
10. Gupta A, Sharma T, Singh SP, Bhardwaj A, Srivastava D, Kumar R. 2023. Prospects of microgreens as budding living functional food: breeding and biofortification through OMICS and other approaches for nutritional security. Front Genet. 14:1053810.
11. Heena, Jindal N, Riar CS. 2025. Microgreens: a comprehensive review on growth conditions, nutritional quality, and their applications. Food Rev Int. 1–33.
12. Hidalgo ME, Bascuñan L, Quilhot W, Fernández E, Rubio C. 2005. Spectroscopic and photochemical properties of the lichen compound lobaric acid. Photochem Photobiol. 81(6):1447–1449.
13. Kello M, Goga M, Kotorova K, Sebova D, Frenak R, Tkacikova L, Mojzis J. 2023. Screening evaluation of antiproliferative, antimicrobial and antioxidant activity of lichen extracts and secondary metabolites in vitro. Plants. 12(3):611.
14. Lone JK, Pandey R. 2024. Microgreens on the rise: expanding our horizons from farm to fork. Heliyon. 10(4).
15. Murugan M, Muthu S, Rajendran K, Ponnusamy P. 2021. UV protection and anticancer properties of lichen secondary metabolites. Sci Acad. 2:1–29.
16. Nethra J, Srinivasulu B, Kumar VV, Rao CS. 2024. Microgreens: a comprehensive review emphasizing urban agriculture. Int J Environ Climate Change. 14(12):154–168.
17. Niazian M, Sabbatini P. 2021. Traditional in vitro strategies for sustainable production of bioactive compounds and manipulation of metabolomic profile in medicinal, aromatic and ornamental plants. Planta. 254(6):111.
18. Pichler G, Muggia L, Carniel FC, Grube M, Kranner I. 2023. How to build a lichen: from metabolite release to symbiotic interplay. New Phytol. 238(4):1362–1378.
19. Pizňák M, Kolarčik V, Goga M, Bačkor M. 2019. Allelopathic effects of lichen metabolite usnic acid on growth and physiological responses of Norway spruce and Scots pine seedlings. S Afr J Bot. 124:14–19.
20. Poulsen-Silva E, Gordillo-Fuenzalida F, Atala C, Moreno AA, Otero MC. 2023. Bioactive lichen secondary metabolites and their presence in species from Chile. Metabolites. 13(7):805.
21. Prado T, Degrave WMS, Duarte GF. 2025. Lichens and health—trends and perspectives for the study of biodiversity in the Antarctic ecosystem. J Fungi. 11(3):198.
22. Rao A, Sharma T, Kaushal S. 2024. Micro-greens: the most impressive and evolving superfood of modern times. Int J Res Agron. 7:208–213.
23. Seth T, Mishra GP, Chattopadhyay A, Deb Roy P, Devi M, Sahu A, Nair RM. 2025. Microgreens: functional food for nutrition and dietary diversification. Plants. 14(4):526.
24. Sosnowski J, Truba M, Vasileva V. 2023. The impact of auxin and cytokinin on the growth and development of selected crops. Agriculture. 13(3):724.
25. Studzinska-Sroka E, Galanty A, Bylka W. 2017. Atranorin—an interesting lichen secondary metabolite. Mini Rev Med Chem. 17(17):1633–1645.
26. Turhan D, Dogan M. 2025. Optimizing soaking time for enhanced microgreen growth in arugula (Eruca sativa Mill.). Int J Adv Nat Sci Eng Res. 9(3):122–127.
27. Upadhyay SK, Rajput VD, Kumari A, Espinosa-Saiz D, Menendez E, Minkina T, Mandzhieva S. 2023. Plant growth-promoting rhizobacteria: a potential bio-asset for restoration of degraded soil and crop productivity with sustainable emerging techniques. Environ Geochem Health. 45(12):9321–9344.
28. Zhou R, Yang Y, Park SY, Nguyen TT, Seo YW, Lee KH, Kim H. 2017. The lichen secondary metabolite atranorin suppresses lung cancer cell motility and tumorigenesis. Sci Rep. 7(1):8136.