From Threat to Opportunity: Harnessing the Invasive Carpobrotus edulis (L.) N.E.Br for Nutritional and Phytotherapeutic Valorization Amid Seasonal and Spatial Variability

Abstract

Carpobrotus edulis (L.) N.E.Br. (Hottentot-fig) is a problematic invasive species found in coastal areas worldwide. Mechanical removal is a common control method, leaving the removed biomass available as a possible source of natural phytochemicals with prospective commercial applications. While the Hottentot-fig's vegetative organs have been studied previously, this work establishes for the first time a seasonal and spatial comparative analysis of its nutritional, chemical, and bioactivity profiles (in three locations over four seasons). Proximate and mineral contents were assessed, along with its phenolic composition and in vitro antioxidant and anti-inflammatory properties. Hottentot-fig's biomass offered a good supply of nutrients, mainly carbohydrates, proteins, and minerals, with a tendency for higher concentrations of the most relevant minerals and proteins in autumn and winter, and in plants from sites A (Ria de Alvor lagoon) and B (Ancão beach). The extracts were rich in polyphenolics, with higher levels in spring and summer, especially for luteolin-7-O-glucoside and salicylic and coumaric acids. The extracts were also effective antioxidants, with stronger radical scavenging activities in spring and summer, along with anti-inflammatory properties. Our results suggest that the usually discarded plant material of this invasive halophyte could be valuable as a source of natural products with potential biotechnological applications in the food and nutraceutical industries.

Keywords: Hottentot-fig; anti-inflammatory; antioxidant; invasive plants; nutrients; phenolics.

Figure 1

Carpobrotus edulis (Hottentot-fig) in southern Portugal: (a) Ria de Alvor lagoon (winter); (b) Ancão beach (spring); (c) Ria Formosa lagoon (autumn). Photos by Catarina Guerreiro Pereira.

Figure 2

Locations of C. edulis (Hottentot-fig) collection in southern Portugal: (A) Ria de Alvor lagoon, (B) Ancão beach, (C) Ria Formosa lagoon. Adapted from Google Maps^® 2021.

Figure 3

Dendrogram representing the Agglomerative Hierarchical Clustering of the seasonal and spatial nutritional profile (proximate composition and mineral content) of C. edulis (Hottentot-fig) aerial parts. (A) Ria Alvor, (B) Ancão beach, (C) Ria Formosa. Wt: winter, Sp: spring, Sm: summer, Au: autumn.

Figure 4

Seasonal and spatial polyphenolic contents (mg/g extract DW (dry weight)) of C. edulis (Hottentot-fig) extracts: (a) total phenolic content (TPC, mg GAE/g DW); (b) total flavonoid content (TFC, mg QE/g DW); (c) condensed tannin content (CTC, mg CE/g DW). Data represent the mean ± SD (n = 6). For each phenolic group, different letters represent significant differences (p < 0.05). GAE—gallic acid equivalents, QE—quercetin equivalents, and CE—catechin equivalents.

Figure 5

HPLC-DAD analysis (320 nm) of C. edulis (Hottentot-fig) extracts throughout the seasons and locations. Peak numbers refer to the compounds in Table 3.

Figure 6

Chemical structure of identified molecules in C. edulis (Hottentot-fig) extracts (Table 3; adapted from Phenol-Explorer 2023 [58]).

Figure 7

Seasonal and spatial anti-inflammatory activity (% NO decrease) of C. edulis (Hottentot-fig) extracts (100 μg/mL). L-Name (200 μg/mL) was used as a positive control (NO decrease: 73.4 ± 4.3%^a). Values represent the mean ± SD (n = 6). Different letters represent significant differences, including the positive control (p < 0.05).

Figure 8

Principal Component Analysis of the seasonal and spatial bioactivities (DPPH, ABTS, NO, FRAP, CCA, RAW) and polyphenolic contents (TPC, TFC, CTC) of C. edulis (Hottentot-fig) extracts, coupled with the nutritional profile (proximate composition and mineral content) as supplementary variables. (A) Ria Alvor, (B) Ancão beach, (C) Ria Formosa; Wt: winter, Sp: spring, Sm: summer, Au: autumn.