Impact of Storage on Bioactive and Toxic Compounds in Jicama (Pachyrhizus erosus) Tubers: Effects on Thyroid Cancer and Inflammatory Responses

Abstract

Background: Jicama (Pachyrhizus erosus) tubers contain isoflavones and phenolic acids with potential chemopreventive and anti-inflammatory effects. This study analyzed bioactive and toxic compounds in fresh jicama tuber (flesh and peel) and assessed changes during freezing for 3 and 4 months. Antioxidant, cytotoxic, and anti-inflammatory effects were evaluated on human thyroid cancer (FTC133, 8505 C, TPC1), and normal cells (Nthy-ori 3 - 1), and RAW 264.7 macrophages.

Methods: High-performance liquid chromatography (HPLC) identified active compounds. Antioxidant activity was tested using FRAP and DPPH assays. Cytotoxicity was evaluated using the MTT assay, while anti-inflammatory effects were measured via TNF-α, IL-6 (ELISA), and nitric oxide levels (Griess assay).

Results: Fresh peel contained the highest levels of isoflavones (mg/100 g dry weight) - biochanin A; 52.5, daidzein; 23.0, genistein; 2.6) and phenolic acids (chlorogenic; 61.7, isochlorogenic acids; 95.8), which declined significantly after freezing. No rotenone was detected. Peel extracts exhibited the strongest cytotoxicity against thyroid cancer cells, particularly FTC133, showing dose-dependent inhibition of cell viability. However, they also exhibited cytotoxicity against normal thyroid cells, highlighting potential risks. Flesh extracts showed weaker cytotoxic effects but demonstrated slightly stronger anti-inflammatory activity than peel extracts. Both extracts effectively reduced TNF-α, IL-6, and nitric oxide levels in RAW 264.7 macrophages. Storage time during freezing had no significant impact on anti-inflammatory activity or cytotoxic potency, but it significantly reduced antioxidant activity.

Conclusion: Jicama peel is richer in bioactive compounds than the flesh and exhibits strong cytotoxic effects on thyroid cancer cells, although it also affects normal cells. Freezing reduces phytonutrient content and antioxidant potential but does not alter anti-inflammatory efficacy.

Keywords: Isoflavones; Jicama; Legume vegetables; Rotenone; Thyroid; Tubers.

Fig. 1

Cytotoxic effect of fresh and frozen (for 3 and 4 months) skin and flesh extracts (100 µg/ml) on normal and thyroid cancer cells. An asterisk (*) indicates a significant difference between cancer cell lines and normal cell lines. An open circle (○) denotes a significant difference between the same frozen and fresh extracts for each respective cell line

Fig. 2

The effect of fresh and frozen (for 3 and 4 months) skin and flesh extracts on: tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and nitric oxide (NO) release in LPS-stimulated RAW 264.7 macrophages. RAW cells were pre-treated with 50 and 100 µg/mL of extracts for 1 h, afterwards cells were incubated with (10 ng/mL) or without LPS (untreated) for the next 24 h. Dexamethasone (DEX) was used as a reference. Values are presented as the mean ± SD (standard deviation) of three independent experiments in triplicate