Symphyopappus reticulatus Baker

The leaves of critically endangered, densely branched, leafy, opposite-leaved, and up to 1 m tall shrub

Symphyopappus reticulatus Baker

(syn. Eupatorium reitzii, S. brasiliensis, S. reticulatus var. vernicosus, S. reitzii) (Koiti and Hattori, 2013)

(April/2005) showed a VO yield comparable to that of leaves of S. casarettoi (0.5%). However, while the latter was characterized by the predominance of hydrocarbon monoterpenes, the former is mainly composed of hydrocarbon sesquiterpenes (63.1%), germacrene D (34.4%), and β- caryophyllene (15.2%) as the major components with 33.9% hydrocarbon monoterpenes, mainly limonene (15.8%), which were found at much lower concentrations on the leaves and inflorescence of S. casarettoi (5.2 and 7.4%, respectively). The VOs obtained from the leaves of the second sample of S. reticulatus (flowering stage, October/2005) were quite similar to those obtained from its leaves during the vegetative period with limonene the only monoterpene observed in a large proportion (12.5%). Hydrogenated sesquiterpenes were predominant in the VOs (63.3%), which were the same major compounds found in the vegetative stage: Germacrene D (23.5%), β- caryophyllene (21.6%), bicyclogermacrene (7.8%), and α- humulene (7.4%). On the other hand, the VOs obtained from the inflorescences of this second sample differed from those obtained from the leaves in the two samples of this species and from the inflorescences of S. casarettoi because it was characterized by a large proportion of oxygenated sesquiterpenes including caryophyllene oxide (16.2%) and spathulenol (14.7%). Among the hydrocarbon sesquiterpenes, the biogenetic-related cluster of β- caryophyllene (29.0%) and α- humulene (9.4%), which usually occur simultaneously, were the major compounds. Monoterpenes were found in very low concentrations (8.6%).

The VOs obtained from leaves of S. reticulatus in the two samples did not present large qualitative and quantitative variations, even in the case of different locations and times of sampling, and different vegetative periods, suggesting that it was not significantly affected by edaphoclimatic variations. A comparison of the VOs obtained from the leaves of S. casarettoi revealed a large quantitative variation, mainly in the monoterpene fraction. Likewise, the VOs obtained from the inflorescences of these two species also showed larger variability. The VO profile of this species was similar to that of the genus Campovassouria. This plant has been reported to be a foraging species for the bee Melipona quinquefasciata (Apidae) (Umpi´errez et al., 2013). A very complex network of interactions between S. reticulatus, other plants, and ants in the subfamilies Myrmicinae, Dolichoderinae, and Formicinae has been described (Costa et al., 2016). Covalane-type diterpenes, as well as from tremetone derivatives, were isolated from the aerial parts of this species (F. Bohlmann et al., 1981). S. reticulatus, together with S. angustifolius, has been recently synonymized under S. braziliensis (Koiti and Hattori, 2013).

The VOs obtained from the 2–6 m tall shrub Symphyopappus itatiayensis (Hieron.) R.M. King & H. Rob. (syn. Eupatorium itatiayense, common name: “vassoura-braba”) (Cabrera and Klein, 1989; King and Robinson, 1987) observed from Minas Gerais to Rio Grande do Sul, Brazil, are surprisingly similar to the VOs obtained from R. tremula with bicyclogermacrene, amorpha-4,7(11)-diene, verboccidentafuran, 3-oxo-verboccidentafuran, and bisabolanes as main components. This plant has been reported to be a host species for bees Apis mellifera, Melissoptila aureocincta, Cephalotrigona capitata, Paratrigona subnuda, Schwarziana quadripunctata, Doeringiella cingillata, Paratetrapedia (Lophopedia) pygmaea (Apidae), Augochlora (Augochlora) amphitrite, A. (A.) caerulior, A. (A.) cydippe, A. (A.) esox, A. (A.) tantilla (Halictidae), and Coelioxys (Acrocoelioxys) tolteca, C. (Rhinocoelioxys) excise, Megachile (Acentron) eburnipes, M. (Austromegachile) trigonaspis, M. (Moureapis) maculate, and M. (Pseudocentron) curvipes (Megachilidae) (Imperatriz-Fonseca et al., 2011; Santos et al., 2017; Weiss, 2008).

From the genus Symphyopappus, only the volatiles from a sample of S. compressus from Parana´State were chemically characterized. They only differed qualitatively from those reported for other species in the genus in the presence of the oxygenated sesquiterpenes mustakone (14%) and cyperotundone (5.5%) (do Amaral et al., 2018), which have copaane and patchoulane nuclei, respectively, while most of the other compounds were similar to those in our samples of S. reticulatus and S. casarettoi. The uniqueness of the chemistry of S. itatiayensis in the genus and its similarity to R. tremula is described for the first time in this study.