Acta Botanica Hungarica 62(1–2), pp. 33–48, 2020 DOI: 10.1556/034.62.2020.1-2.4

THE AMOUNT OF SECONDARY METABOLITES IN CLADONIA FOLIACEA (, LICHENISED )

E. Farkas1*, B. Biró1, K. Szabó1, K. Veres1,2, † Zs. Csintalan2 and R. Engel1 1Laboratory for Lichenology and Phytochemistry, Institute of Ecology and Botany MTA Centre for Ecological Research, H-2163 Vácrátót, Alkotmány u. 2–4, Hungary E-mail: [email protected], *corresponding author 2Institute of Botany and Ecophysiology, Szent István University H-2100 Gödöllő, Páter K. u. 1, Hungary

(Received 13 October 2019; Accepted 28 November 2019)

The terricolous species Cladonia foliacea (Cladoniaceae, lichenised Ascomycota) widely distributed in open, dry lowland steppe and rocky mountain grassland vegetation in Eu- rope was chosen as a potential test organism for ecological experiments, since their thalli are producing cortical solar radiation-protective and UV screening pigment dibenzofuran usnic acid and medullary secondary substance depsidone fumarprotocetraric acid. Sig- nificant seasonal differences were found in the amounts of lichen secondary metabolites analysed by HPTLC and HPLC-PDA between summer and winter collected thalli in sandy grassland area in Hungary. The concentrations of usnic acid varied between 7.34 and 15.52 mg/g in summer collected samples and 13.90 and 21.61 mg/g in winter collected ones. A comparable amount (11.61±0.29 mg/g) was measured in pulverised samples. The concen- trations of fumarprotocetraric acid varied between 0.60 and 3.01 mg/g in summer collected samples and 2.26 and 5.81 mg/g in winter collected thalli. A comparable amount (2.45±0.21 mg/g) was found in pulverised samples. The range of concentration values is comparable with data known from . A higher amount of usnic acid is produced in winter prob- ably to ensure sufficient protection also for summer. The fumarprotocetraric acid content of the medulla might contribute to the solar irradiation reflecting role of the pale lower surface lobes turning upwards in dry condition.

Key words: acetone rinsing, chlorolichens, fumarprotocetraric acid, high performance liq- uid chromatography with photodiode array detector (HPLC-PDA), seasonal differences, usnic acid

INTRODUCTION

Lichenised associations represent a sensitive model ecosystem for in- vestigating various or changed environmental conditions (cf. Asplund et al. 2017, Bergamini et al. 2005, Galloway 1993, Nash 2008, Stofer et al. 2006). Li- chens produce a great variety of lichen secondary metabolites (LSMs), and most of them are unique to lichen-forming fungi as it is summarised in recent reviews on their biological roles (Calcott et al. 2018, Molnár and Farkas 2010).

© 2020 The Authors

Unauthenticated | Downloaded 09/26/21 12:53 AM UTC 34 FARKAS, E., BIRÓ, B., SZABÓ, K., VERES, K., †CSINTALAN, ZS. and ENGEL, R.

Approximately 1,050 secondary compounds have been identified to date (Stocker-Wörgötter 2008, 2015). These chemically diverse (aliphatic and aro- matic) lichen substances are produced by the mycobiont (Elix 1996, Huneck 1999). Some of them (such as atranorin, parietin, usnic acid or fungal mela- nins) are accumulated in the cortex, others (such as norstictic acid, physodic acid, physodalic acid, protocetraric acid, etc.) are detected as tiny extracellular crystals within and on the proteinaceous hydrophobic wall surface layer of the hyphae in the medullary and photosynthetic layer (also on photobiont wall surface) (Honegger 1986, 1997, 2012). Lichen secondary chemistry analyses – and study of their relation to en- vironmental conditions (cf. Armaleo et al. 2008, Asplund et al. 2017, Hauck 2011, Hauck et al. 2009, Matteucci et al. 2017, Shukla et al. 2016) – clarify the background of the chemical diversity of the studied taxa. Mos