乾燥方法對新品種洛神花的化學成分及生物活性影響研究

Abstract

洛神花作為臺灣常見的天然食材，廣泛種植於花東地區，民間常用其鮮紅色果萼調節血壓、治療肝臟疾病、抗發炎和控制血糖等。臺東農改場透過雜交育種技術，培育出富含花青素的洛神花新品種臺東6號。目前仍缺乏其化學組成分及功能性方面的報告，因此本研究目的為探討不同乾燥條件對新品種洛神花的化學成分及生物活性影響。本實驗採用三種乾燥方法，包括冷凍乾燥、50°C熱風乾燥 (48小時) 及60°C熱風乾燥 (24小時)，並對樣品中酚類、黃酮類、花青素等活性成分的含量及其抗氧化、抗發炎、抗肥胖和美白等生物活性進行系統性分析，且以傳統種植的臺東3號作為對照組。洛神花經清洗、去籽、乾燥和均質化處理後，以高極性溶劑 (甲醇和丙酮) 和中極性溶劑 (乙酸乙酯) 分別進行萃取，並採用HPLC-ESI-QTOF MS/MS和GC-MS方法鑑定樣品中的成分。生物活性評估利用DPPH、ABTS和FRAP三種方法測試樣品的抗氧化能力，並透過細胞實驗測定抗發炎、美白和抗肥胖效果。結果顯示，臺東6號的總酚類和總黃酮類含量顯著高於臺東3號，然而不同乾燥方法對其影響並不顯著，說明酚類化合物和黃酮類具有較強的熱穩定性。相較之下，花青素含量則顯著受到乾燥溫度的影響；冷凍乾燥方法能保留最多的花青素，而50°C熱風乾燥樣品中的花青素含量最低，這可能是由於高溫長時間處理導致花青素分解或氧化所致。生物活性的分析結果顯示，處理條件對洛神花萃取物的DPPH、ABTS自由基清除能力和FRAP還原力的影響不明顯，各處理組間的差異不顯著，顯示乾燥方法對洛神花的抗氧化效果影響較小；此結果與總酚類含量的結果相符，表明總酚類含量是抗氧化能力的重要指標。洛神花萃取物能顯著抑制脂多醣活化之RAW264.7巨噬細胞的一氧化氮、TNF-α及IL-6生成，並呈現良好的劑量效應，而臺東6號的抗發炎效果優於臺東3號，此與臺東6號有較高的總酚類和總黃酮類的含量有關，較多的酚類及黃酮類化合物為臺東6號提供良好的抗發炎能力，其中臺東6號經長時間較低溫熱風乾燥 (50°C) 的抗發炎效果最佳。美白活性顯示臺東6號對黑色素生成具有顯著抑制效果，並能降低黑色素瘤細胞B16F10中的酪胺酸酶活性，說明具有良好的美白潛力。臺東6號也能有效抑制脂肪細胞中的油滴累積，顯示其在控制體脂生成方面的潛在應用價值。LC-MS/MS正離子模式與負離子模式分析共鑑定出30種化合物，主要為酚酸、黃酮類及花青素。主成分分析結果發現，新品種的臺東6號與傳統栽培的臺東3號代謝物輪廓有明顯差異，且乾燥方式對兩品種洛神花的化學組成影響顯著。成分熱圖結果顯示，抗發炎活性成分含量在較低溫 (50°C) 的熱風乾燥下會有所提升，進而促進抗發炎的效果。氣相質譜儀共鑑定出27種化合物，主要可分為醇類、醛類、酮類、酯類、有機酸類及烷烴。成分熱圖顯示不同乾燥處理方法對洛神花揮發性成分的含量影響顯著，其中冷凍乾燥能保留較多的揮發性成分。綜上所述，臺東6號洛神花具有豐富的機能性成分及良好的生物活性，尤其在抗氧化、抗發炎、美白和抗肥胖等方面表現突出。而不同的乾燥方法在生物活性上具有不同的優勢，冷凍乾燥可以保有最多的花青素，熱風乾燥可以提高抗發炎及抗肥胖的功效。本研究成果不僅說明臺東6號作為保健產品的價值，也為洛神花加工產業提供較佳乾燥方法的選擇依據。

Roselle (Hibiscus sabdariffa L.), a common natural ingredient in Taiwan, is widely cultivated in the Hualien and Taitung regions. Its bright red calyces are traditionally used for regulating blood pressure, treating liver diseases, reducing inflammation, and controlling blood glucose levels. The Taitung Agricultural Research and Extension Station has developed a new anthocyanin-rich cultivar, Taitung No. 6, through hybrid breeding. However, there is a lack of reports on its chemical composition and functional properties. Therefore, this study aimed to investigate the impact of various drying conditions on the chemical composition and bioactivities of this novel cultivar, Taitung No. 6.Three drying methods were employed in this study: freeze-drying, hot air drying at 50°C for 48 hours, and hot air drying at 60°C for 24 hours. The contents of active compounds such as polyphenols, flavonoids, and anthocyanins, as well as their antioxidant, anti-inflammatory, whitening, and anti-obesity activities, were systematically analyzed. The traditional cultivar, Taitung No. 3, was used as the control group. After washing, deseeding, drying, and homogenizing the roselle samples, extraction was carried out with high-polarity solvents (methanol, acetone) and medium-polarity solvent (ethyl acetate). The chemical composition of the extracts was identified using HPLC-ESI-QTOF MS/MS and GC-MS. Biological activities were assessed by testing antioxidant capacity using the DPPH, ABTS, and FRAP methods, and by evaluating anti-inflammatory, whitening, and anti-obesity effects through cell assays. Results revealed that Taitung No. 6 had significantly higher total phenolics and total flavonoids contents than Taitung No. 3. However, different drying methods did not significantly affect these compounds, indicating that phenolics and flavonoids have strong thermal stability. In contrast, anthocyanin content was significantly affected by drying temperature; freeze-drying preserved the most anthocyanins, while hot air drying at 50°C resulted in the lowest level, likely due to prolonged high-temperature treatment leading to anthocyanin degradation or oxidation. The results of the bioactivity analysis showed that the drying methods had minimal effect on the DPPH and ABTS radical scavenging capacity and the FRAP reducing power of roselle extracts, with no significant differences between the groups. This indicates that drying methods have a limited impact on the antioxidant effects of roselle. These results are consistent with the total phenolic content findings, suggesting that total phenolic content is an important indicator of antioxidant capacity. The roselle extract significantly inhibited nitric oxide production in lipopolysaccharide-activated RAW264.7 macrophages, displaying a good dose-response effect, and Taitung No. 6 exhibited superior anti-inflammatory activity compared to Taitung No. 3. This was related to the higher total phenolics and total flavonoid contents of Taitung No. 6, as these compounds provide excellent anti-inflammatory capabilities. Among the different drying methods, the anti-inflammatory effect of Taitung No. 6 was most pronounced when subjected to prolonged low-temperature hot air drying (50°C). Whitening activity demonstrated that Taitung No. 6 effectively inhibited melanin production and reduced tyrosinase activity in B16F10 melanoma cells, showing its strong whitening potential. Taitung No. 6 also effectively suppressed lipid droplet accumulation in adipocytes, highlighting its potential in controlling adipogenesis. LC-MS/MS analysis identified 30 compounds in both positive and negative ion modes, which were primarily phenolic acids, flavonoids, and anthocyanins. Principal component analysis revealed distinct differences in the metabolic profiles of Taitung No. 6 and Taitung No. 3, with drying methods significantly affecting the chemical composition of both cultivars. Heatmap results indicated that the content of anti-inflammatory active compounds increased under lower-temperature (50°C) hot air drying, thus promoting anti-inflammatory effects. GC-MS analysis identified 27 compounds, primarily including alcohols, aldehydes, ketones, esters, organic acids, and alkanes. The heatmap results showed that different drying methods significantly influenced the volatile compound content of roselle, with freeze-drying preserving more volatile compounds. In conclusion, Taitung No. 6 roselle was rich in functional compounds and possessed remarkable bioactivities, particularly in antioxidant, anti-inflammatory, whitening, and anti-obesity properties. Different drying methods offered distinct advantages: freeze-drying preserved the most anthocyanins, while hot air drying enhanced anti-inflammatory and anti-obesity effects. This research not only highlighted the value of Taitung No. 6 as an ingredient for functional product development but also provided valuable guidance for an optimal drying method in the roselle processing industry.