Phyto-compounds and pharmacological activities of Lygodium lanceolatum Desv. (Schizaeaceae)

Lygodium lanceolatum Desv. (Schizaeaceae) is a native fern of Madagascar and Comoros. This species is widely used by the Malagasy population for the treatment of several diseases including different categories of pain. This work aims to determine the antioxidant capacity, the analgesic and anti-inflammatory properties of this plant and to report its phytochemical composition related to therapeutic properties. The methanol extract (MELL) and aqueous decoction (DLL) were prepared from the L. lanceolatum aerial parts. The isolation of compound 1 was carried out using exclusion chromatography. The total polyphenolic content (TPC) was evaluated using the Folin-Ciocalteu assay. Different HPLC methods were performed to quantify bioactive compounds in the L. lanceolatum aerial parts. The antioxidant capacity was determined using the DPPH free radical scavenging method and the Ferric Reducing Antioxidant Power (FRAP) assay. In vivo carrageenan-induced mice paw oedema was used to evaluate the anti-inflammatory activity, while the evaluation of the antalgic activity was carried out by the in vivo acetic acid-induced writhing test in mice. Acute toxicity was performed in mice to evaluate the toxicity of methanol extract and decoction of L. lanceolatum. The aerial parts of L. lanceolatum showed a high level of total polyphenolic content with a mean value of 10168.47 ± 1117.09 mgGAE/100 g of dry weight (DW). The HPLC total bioactive compound content (TBCC) showed a value of 4181.59 ± 1485.2 mg/100 g DW. Organic acids represent 79.12% of TBCC: malic acid (45.45%), succinic acid (12.02%), and quinic acid (11.47%) are the main quantified compounds. The isolated compound 1 was quercitrin which represents 1.12% of TBCC. Isolated quercitrin and MELL potently inhibited the free radical DPPH more than DLL. MELL antioxidant capacity was confirmed by the FRAP results. MELL, as well as DLL, inhibited in a dose-dependent manner the carrageenan-induced paw oedema and the acetic acid-induced writhing in mice. Quercitrin was 20 times more effective than DLL to decrease the number of writhes. MELL and DLL did not demonstrate toxicity during the acute toxicity test. These results indicate that L. lanceolatum possesses strong antioxidant, anti-inflammatory and antalgic properties thanks to phenolic compounds and organic acids, in particular quercitrin (the isolated compound) confirming the wide use of this species in the popular Malagasy medicine.