Antiallergic activities of shallot (Allium ascalonicum L.) and its therapeutic effects in allergic rhinitis

Warangkana Arpornchayanon,¹ Soraya Klinprung,¹ Sunee Chansakaow,² Nutthiya Hanprasertpong,¹ Saisawat Chaiyasate,³ Masaaki Tokuda,⁴ Hirotoshi Tamura⁵

¹ Department of Pharmacology, Faculty of Medicine, Chiang Mai University, Thailand
² Department of Pharmaceutical Sciences and Medicinal Plant Innovation Center, Faculty of Pharmacy, Chiang Mai University, Thailand
³ Department of Otolaryngology, Faculty of Medicine, Chiang Mai University, Thailand
⁴ Faculty of Medicine, Kagawa University, Japan
⁵ Department of Applied Biological Science, Faculty of Agriculture, Kagawa University, Japan

Abstract

Background: Onion has antiallergic activity but lack of evidence for shallot.
Objectives: To determine whether shallot owns similar antiallergic activity to onion and its therapeutic effects in allergic rhinitis when added to standard treatment
Methods: In-vitro β-hexosaminidase inhibitory activities of shallot was compared with onion on RBL-2H3 cells. In clinical study, a randomized, double-blind, placebo-controlled trial was performed. Sixteen AR patients were randomized equally into the controls who received cetirizine 10 mg once daily and placebo capsules for 4 weeks, and the treatment who received 3 g of oral shallot per day (equivalent to 1 ½ bulbs) and cetirizine. Visual analog scores of overall symptoms (VAS), total nasal and ocular symptom scores (TNSS and TOSS), nasal airway resistance (NAR), and adverse events were assessed.
Results: Shallot extract at 200 μg/mL had an average β-hexosaminidase inhibition rate of 97% while onion extract had 73%. HPLC chromatograms (λ = 290 nm) of both plants showed nearly identical patterns of quercetin compounds, such as quercetin 3,4’-diglucoside, quercetin 4’-glucoside, and quercetin. After 4-week of treatment, 62.5% of patients in shallot group and 37.5% of patients in control group showed improvement of post-treatment VAS. TNSS were significantly reduced in both groups, however no difference between groups (P = 0.18). TOSS were significantly improved only in the shallot group (P = 0.01). Adverse events from shallot were not different from placebo.
Conclusions: Shallot had antiallergic activity and similar quercetin compounds to onion. The shallot oral supplement and cetirizine was shown to improve the overall AR symptoms more than cetirizine alone.
Key words: Allergic rhinitis, onion, shallot, Allium ascalonicum L., Allium cepa